The Best Way to Power Your Railway | Third Rail vs. Overhead Wire

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[@RMTransit]

This video a remake of a previous video incorporating viewer feedback and fully revamping the visuals and rewriting the script (for more details, see my recent community post). Please enjoy and consider sharing!

[@georgobergfell]

I like this video a lot better than the original one 👍🏻

[@erikwilliams8610]

Please make a follow up explanation video about the Alstom APS and why it doesn't work for temperate climates The information is sparse and the concept is fascinating.

[@marcogeurts9881]

@RNTransit in The Netherlands the RET Metroline E rides from Den Haag Centraal to Slinge and from Den Haag Centraal until metrostation Melanchtonweg the metro use Overhead Wires and at the station Melanchtonweg while it halt at the station it switches to third rail and then it uses from Melanchtonweg until Slinge third rail from the Rotterdam Metro system and it shares the tracks from Den Haag Laan van Nieuw Oost Indie until Leidschenveen Tram/Metrostation with HM Randstadrail line 3 from Den Haag Loosduinen to Zoetermeer Centrum-West and 4 from Den Haag De Uithof to Langslingerland Zoetermeer and they use then the former Hofpleinlijn and the trams also the former Zoetermeerlijn. And by RET metroline A from Binnenhof metrostation it use overhead wires from Binnenhof metrostation until Capelsebrug and Metroline B use from Nesselande metrostation until De Tochten metrostation third rail and then by De Tochten it changed to overhead wires and then from De Tochten until Capelsebrug it use overhead wires and halfway by the crossing by metrostation Graskruid metroline A joins metroline B to Capelsebrug and then together it goes to Schiedam Centrum running together with metroline C until Schiedam Centrum and metroline A and B are switching while driving to Schiedam Nieuwland from third rail to overhead wires and from Schiedam Nieuwland until Vlaardingen West metroline B runs together with metroline A and sometimes a freight train until Vlaardingen Oost and the metroline B runs to the temporary metrostation Hoek van Holland Haven where it ends on 1 of the former train platforms where in 1935 until 1994 D train international teaibs deprted and until 2017 local trains to Rotterdam Centraal departed. Metroline C runs from De Terp to De Akkers where it shares tracks from Capelsebrug until Schiedam Centrum with RET metrolines A and B where line A and B runs then to Vlaardingen West and Hoek van Holland Haven and metroline C runs then further to metrostation Tussenwater where it shares until metrostation De Akkers where it ends the tracks with Line D wich runs from Rotterdam Centraal and shares the track to Slinge with Line E from Den Haag Centraal and metrostation Beurs is a metrostation where at Beurs you can change from Metroline A to Vlaardingen West and Binnenhof to metrolines B to Nesselande and Hoek van Holland, metroline D from Rotterdam Centraal to De Akkers, metroline C from De Terp to De Akkers and metroline E from Den Haag Centraal to Slinge. Maybe you can make a video about the Rotterdam Metro

[@1121494]

Hello Mr. Martin, thank you for the remake. However you apparantly still just do a comparison and no clear verdict of which type of electrification, voltage and frequency is the best and should be built for all types of trains in the future. Could you maybe still state a verdict on that? Best regards,

[@doorhanger9317]

This is a much more thorough comparison than the last video, but thing you still didn't mention (and I can imagine fair reasons why you wouldn't) is cost. Third rail does involve less structural components and less copper, with modern systems mainly relying on relatively accessible aluminium. With modern tech, it could simply be incorporated into slab track. This means that there's some benefit to resource use and embedded carbon, at least on the denser systems where third rail is best suited, even if some may argue the actual financial advantage. This can also mean less maintenance if the RoW is protected, which can be another cost saving. This is why I'm something of a third rail defencist, since on grade-separated metros using a 1500V bottom-contact system, you ditch most of the disadvantages but retain all of the advantages, and I think it should really be the standard for new metro systems, especially since it's easy to combine with traditional 1500V overhead in particular areas, as you mentioned.

[@aapjeaaron]

One day there will be a train management sim where you have to decide what type of electrification you use only to curse yourself that you need to adapt your new trains to run on old electrification standards.

[@user-wx6mi5xh7w]

We sort of have that, unfortunately. It's called Cities: Skylines. I'm still pissed I can't do, say, Toyoko/Fukutoshin/Seibu Ikebukuro/Tobu Tojo or Crossrail-esque services in the game because there are no underground "train" stations, for fuck's sake.

[@jamesh5019]

NIMBY Rails?

[@Sneder]

How about OpenTTD, not in the base game, but there's even dual mode dual gauge tracks in the Mods. The base game also doesn't really exist cuz everyone mods it

[@RMTransit]

Sims exist to make the most frustrating real life infrastructure challenges into an entertaining puzzle!

[@Zosu22]

@@user-wx6mi5xh7w there are underground train stations on the workshop

[@Muzer0]

It's high voltages that are more efficient at transmitting power over long distances, rather than this being something inherent about AC. In fact, DC is actually more efficient at transmitting power than AC, but this is overshadowed by the difference between voltages - this is why a lot of modern high voltage power links use DC. The reason that high voltages are traditionally associated with AC though is that up until relatively recently, it was just impossible to handle high voltage DC affordably and practically. AC can very easily be changed in voltage using a transformer, whereas DC needs modern power electronics to change the voltage. So why is high voltage more efficient? Well, P=IV tells you that for a given amount of power that needs to be delivered, if your voltage increases, current will decrease (I = P / V). Now if we take R to mean the resistance of the *wire* rather than the load, P = I^2 R tells us that for a given value of current, power loss in the wire will be greater, in fact proportional to the square of the current. So increasing the voltage dramatically reduces power lost. This is why power transmission lines tend to be very high voltage. OK, so why isn't third rail high voltage if it's more efficient? Simple - because it's close to the ground, the return path, and potentially humans, it's neither safe nor practical to make it much higher voltage than maybe 1000V or so. Most third rail I know of is in about the 500-750V range. So why build third rail in the first place if it's so much less efficient? Well, this comes down to another difficulty of AC vs DC. In the early days of rail electrification, there was no practical way to convert from AC to DC on a train. Why would you want to do this? Again in these early days, AC motors could only be made to go at one speed which was governed by the frequency of the AC power. This is not good for a train, so instead they used DC motors, which are more expensive to maintain but would allow for easy changing of speed by doing things like switching resistors in and out of the circuit. So at this point your only choice is DC distribution - and with DC distribution your only choice at this point was low voltage. The Germans actually came up with a clever way around this - it turns out that low frequency AC can be used to drive traditional DC motors, with a bit of modification. So they used low frequency AC to power their trains, 15kV AC @ 16.7Hz. What's the trade-off here? With lower frequency AC you need much larger transformers to convert the voltage. This trade-off was considered worth it. But in other countries, they went with relatively low voltage DC transmission, either through third rail or overhead lines. Of course, they were often only building very urban electrification systems at first, so the power losses didn't matter much. This is also why they still build new metro systems with third rail - you're just over such a small area that having to have more substations and more power loss is not worth the hassle of going with AC. But for long-distance lines, the power losses start to get significant. Then around the 50s, technology like mercury arc rectifiers, soon after giving way to solid state rectifiers of various sorts, could now be fitted on trains. This would allow AC to DC conversion to happen on trains. This means you can now have high voltage efficient transmission at normal mains frequencies, convert it down to low voltage for your motors, and rectify to DC. This is about when the 25kV AC @ 50Hz (or 60Hz depending on the local mains frequency) standard emerged for overhead wires, a standard used across large parts of the world to this day. Of course many countries still retain their legacy systems as well, and perhaps only use 25kV on new high speed lines, if at all. But it's heavily used in large parts of France and Britain, and many places that didn't have a serious electrification programme until a significant time after WWII. As far as I know after the technology was proven in Britain and France, no country has chosen anything else for a completely new-build electrification system for a long-distance rail network where there hasn't been a need for compatibility with some existing electrification. What else has changed? Remember I said that DC motors are harder to maintain than AC ones? Well, advances in power electronics in the 1990s have allowed DC motors in trains to give way to AC motors. This basically involves using power electronics to change the frequency of the AC as required to change the speed of the motors. Nowadays most trains, even ones designed to run on DC power, will have AC motors; obviously the DC will be converted via power electronics to AC to power the motors. Many trains since the early 90s and most trains since the 2000s have been built like this.

[@albertomontante]

Wow you did an excellent job at explaining the crucial differences and advantages, I couldn’t have done it better. I hope many people will read this in order to prevent false information to be spread

[@stephanweinberger]

A small addition to the last paragraph: in all modern locomotives the variable-frequency current for the motors is derived from a DC intermediate circuit. This has the added benefit that it makes it very simple to build multi-system locomotives that can run under different types of electrification. In a DC network the power from the overhead wire is just fed directly to the intermediate circuit, whereas under AC overhead lines it will be transformed to an appropriate voltage and rectified (so even the frequency doesn't matter all that much nowadays, it just slightly affects how the transformer needs to be built). Another thing that's common nowadays is energy recovery (i.e. using the motors to generate power while braking and feeding that power back into the grid). Basically it uses very similar electronics not only on the motor side but also at the power feed, in order to match the voltage & frequency of the grid when feeding back power.

[@Robbedem]

a funny thing is that you can recognise AC motors on trains by their sound. (Basicly all modern trains) When they leave a station, you will hear them humming at different tones, going from low to high. That's the electronic controller increasing the frequency, of the AC power to the motors, increasing their speed.

[@doorhanger9317]

As an interesting additional fact, the German solution of AC drive to DC motors wasn't just used in the Germosphere, it was also the predominant system on American catenary, in its heyday. There wasn't much of a choice, since the US was electrifying long-distance, high-speed lines in the days before rectifiers and the grid-frequency standard. This is why, to this day, large parts of the overhead electric networks in the US northeast still run on their own, separate, 25Hz power grids, with traction power supplied at 12kV, although I think historically it was 11kV.

[@stephanweinberger]

@@doorhanger9317 Yes, in the early days of AC electrification there were all kinds of voltage/frequency combinations. Basically almost every new project tried to push the envelope of what was technically possible and experimented with a new combination. E.g. here in Austria the first line electrified with AC power was the Stubaitalbahn in 1904, which initially used 2.5kV/42.5Hz (which was later changed to 3kV/50Hz - to make use of the 50Hz power grid -, and finally to 900V/DC when the line was integrated into Innsbruck's tram network). The Mariazellerbahn, which was electrified only a fews years later (1911), uses 6.5kV/25Hz to this day. Meanwhile the national railways followed the German and Swiss example and used 15kV/16.7Hz from the start. And of course there are various local lines which were electrified sometime in the late 19th and early 20th century that to this day continue to use DC power at various voltages between 750V and 1.8kV. Curiously we also have 25kV/50Hz lines in the east: the GySEV (a rail company with very interesting history btw., as it kept operating cross-border services even during the cold war) used the Hungarian system when they electrified their line in the late 80s. Also the Brenner base tunnel will be electrified with 25kV/50Hz, despite all connecting lines using either 15kV/16.7Hz (Austria) or 3kV/DC (Italy). This only shows how far power electronics have come, and that today it basically doesn't matter anymore which system you use.

[@wtspman]

One of the main benefits of electrification (vs systems where the power is generated on board the train), regardless of the mode of collection. is the ability to adapt the power supply to different sources of generation without having to change your fleet of rolling stock. You can switch to cleaner, more efficient technologies as they come along, and the railways and transit providers are unaffected. You can contrast this with the costs North American freight railways have had to bear as new pollution standards for diesels have been implemented. New standards mean newer, more expensive locomotives.

[@luislicona386]

Does anyone know what would be required for an electrified freight train to work?

[@catprog]

Electrification of the railroad. Same as the passenger trains.

[@GintaPPE1000]

That’s a little disingenuous of an example. as EPA standards only apply in full force to new diesel locomotives. Railroads simply either bought as many locomotives as they could before Tier 4 took effect, or stepped up rebuilding programs and bought older engines back from lessors in order to take advantage of grandfathering clauses in EPA mandates. The reason they’re buying fewer locomotives these days is a combination of this long-term “motive power banking” strategy and a downturn in commodity traffic that started with COVID, but hasn’t abated yet. It should also be pointed out that Tier 4 freight diesels burn more fuel as they use less-efficient combustion to reduce NOx emissions, rather than DEF. That’s cheaper than the DEF that Amtrak and most commuter agencies resigned themselves to using, but not as cheap as just keeping Tier 3-compliant and older diesels in service.

[@jakenguyen7463]

If anyone else is curious like I was, the reason why the pantographs don't ruin the wires and themselves with friction when trains are going at such high speeds is the contact point uses graphite. Graphite is both a solid lubricant and electrical conductor. When it wears down they simply replace the contact point on the pantograph and the wires above are just fine.

[@theelectricwalrus]

I've seen the MBTA blue line change modes from third rail to catenary! It happens at airport station

[@madcrowmaxwell]

Strangely, when the extension to Wonderland was first built, the switchover happened at Maverick. The train used the overhead the entire time it was above ground. For some reason they moved the switchover point to Airport at some point in the 70s or 80s (Maybe when the Hawker-Sidley stock came online). The last time I was up that way, the overhead still continued all the way to Maverick, though.

[@RMTransit]

Yeah! Its not a huge production which I enjoy

[@nathanieldaiken1064]

NYC Metro North and NYNHH&CT have dual modes: catenary and underslung third rail

[@derpasaurus_rex6919]

This may be a bit of a controversial view, but I actually like how overhead wires look, along with the pylons. If done right, it can give a sort of futuristic feel to a railway.

[@machinismus]

I agree! I’ve always thought they looked cool. when I’m older I will find a discounted house by a power substation or a pylon trail.

[@p1xel1115]

Yeah, the pylons do look nice

[@pelpikx]

I also agree, Wires look nicer and are safer

[@user-pv6qk6rm2u]

Interesting fact: only third rail subway lines have their well known smell because the graphite from the contact shoes wear out and the poor ventilation on sublevel lines create the distinctive smell

[@technoman53]

I work for the Washington DC Metro. I just wanted to point out a few details about 3rd rail you missed. 1. The main reasons 3rd rail switches sides is to separate sections so they can be shut off in individual segments instead of the whole line, also it evens out the wear on collector shoe. 2. On a bottom contact system the top and sides are still live as it's a solid piece of metal, also the bottom and sides of the third rail are the most likely places to accidentally touch with your foot, not the top. 3. For inclement weather there is heater tape on the rails. Also we have special deicer flatcars that have insulated scrapers to scrape ice off the 3rd rail and spray nozzles for glycol antifreeze. Additionally in extreme conditions the revenue cars can also be outfitted with glycol sprayers. 4. In the yards there is 3rd rail. However inside the railcar shops there is something called a "stinger", which is basically a 750 volt jumper cables hanging from a track on the ceiling. It's got a clamp on the end that a mechanic wearing insulated gloves will attach to a collector shoe. This is probably what they're talking about for the Chinese metro yards.

[@pizzajona]

What type of third rail is in DC? Also, unrelated question, WMATA has already had to slow the trains a couple times this year because of hot weather expanding the rail. As someone who seems to know WMATA’s infrastructure well, do you know how this can be dealt with better?

[@technoman53]

@@pizzajona We use top contact 750 volt dc third rail. As for the speed restrictions, unfortunately the laws of physics and metallurgy work the same in DC as anywhere else. The reason for the restriction is that if there is a sun kink the operator can hopefully see it and stop the train in time to prevent a serious derailment. We use 100% continuously welded rail with pandrol clip fasteners, so we are a bit more susceptible to sun kinks than other transit systems that still use jointed rail and spikes.

[@pizzajona]

@@technoman53 thanks, that’s very helpful! Is there something other transit agencies in hot climates do that can help WMATA? Or do new lines need to be built underground to fully solve this issue?

[@cieludbjrg4706]

@@pizzajona Oslo used to use a somwhat milder (softer) steel than running rails (and also a different profile & weight). They have now started to replace steel with aluminium, since aluminium is lighter and also is a better conductor than steel. I guess that makes for a lighter third rail, which probably has some benefits, and for less losses, or the ability to provide more peak power. Engineers usually have good reasons for such changes. :)

[@cieludbjrg4706]

Interesting. Oslo almost exclusively has the third rail in the middle (to the left) of the track. It only switches to the right in a few tight curves, and in switches. However, since trains switch tracks at the end stops, the contact shoes get even wear. Oslo also uses under-contact (as does the Berlin S-Bahn), as opposed to Stockholm, who uses top contact (like New York & London "overground"). Since Stockholm started service maybe 10 years before Oslo, the engineers might have had a look at the difficulties you’ll encounter with top contact & snow & ice, and decided on under-contact. (Or they might have decided on under-contact as safer for people & animals straying on the tracks).

[@SilverDragonJay]

Interesting. I like the idea of using third rail below ground and then swapping aboveground to make it safer for people. Also the idea of having the power lines oscillate to spread wear out. That's one of those subtle little design features that I'm sure was a big "oh duh" moment when someone came up with it.

[@keacoq]

I suspect it may have started as something easier than making them straight. When they zigzag a little I think you can have better control over the tension, because it is easier to see what is going on. I'm no expert, though.

[@TommyTom21]

Yeah the blue line in Boston does this, uses third rail underground and then switches to a pantograph above ground.

[@sobu_hasy]

10:40 this approach of using catenary in the train yard to protect the workers is used on the Bucharest Metro system in Romania. On normal service, the Bucharest Metro uses third rail power at 750V DC, while on train yard it is used low-power overhead lines at 230V DC, where the maximum speed is at 15 kmh!

[@jonathanj8303]

British Rail Southern Region (and its predecessor the Southern Railway) did something similar up to a point. The vast majority of the system was 750V DC 3rd rail, including all the passenger emu depots and stations, but a handful of outlying freight yards were fitted with tramway style super-light catenary instead (still 750V DC) to make the ground safer, and the class 71 locos had pantographs so they could run on it to access/switch the non-3rd rail areas. (The SR Bulleid electrics had pantographs too, but there were only 3 of them vs I think 24 cl71's.)

[@delonperera7849]

Milan also does this with their M1 and M3 metro lines.

[@paupadros]

Rigid Catenary in urban tunnels with regular catenary in the open seems like the best overall option to me. Does anyone know what Crossrail uses in tunnels? It seems to be rigid catenary but with catenary poles? Odd

[@RMTransit]

IIRC rigid is used in some places, there are not full poles in the tunnels though! You can see in the POV videos!

[@K-o-R]

Definitely rigid bar in the tunnels.

[@fetchstixRHD]

You can see the rigid bar used in the tunnels in the Crossrail Project's December 2020 cab view!

[@paupadros]

@@fetchstixRHD Yes, rigid bar for sure. I'm talking about what is holding the rigid bar. Seems to be a bit more complex than what I've seen used here in the Barcelona metro for instance.

[@K-o-R]

@@paupadros in this case it's basically just a three-section bar connected between the roof and the conductor rail, the centre section being the common brown insulators.

[@joegrey9807]

It's basically the battle between the 'coat-hanger and knitting' or the 'stabiliser rail'. To be honest, nowadays it's easy enough to have trains that can do both. A lot of UK trains either have both fitted, or are designed so that the other system can be retrofitted relatively easily.

[@dasy2k1]

Technically Catenary refers only to the top of the 2/3 wires in a typical OHLE system due to the shape it follows. The wire that the pantograph actually touches is called the contact wire (and droppers connect the 2) When there is only 1 wire as in a tram system its generally referred to as a trolly wire regardless of whether pantographs or trolly poles are used (or both as per Toronto)

[@MervynPartin]

Absolutely correct. Further to that, the technical term Catenary actually refers to the physical shape assumed by a a rope, cable or wire under gravity from its anchors at each end and a rigid overhead conductor rail should never be described as Catenary.

[@amtorraziert]

It may just be me but I like the appearance of the catenary. In Germany the Green Catenary poles have become a Staple and it's hard to find anyone who actually considers them obtrusive

[@goatgamer001]

I really like cantenaries too they are beautiful

[@gardenman3]

And I think overhead is ugly.

[@RMTransit]

Its not the end of the world, but I don't think its beautiful!

[@hypernewlapse]

@@RMTransit it has a certain charm, especially in a quaint euro street with cobblestones. Defo it doesn’t look that nice in an American stroad

[@Bcerto]

Thanks RM! Love all of your videos but especially love these educational breakdowns. As a transportation geek in training I found this extremely helpful 🙏🙏🙏

[@timothymeyer3210]

Pre-60s trams extensively used centre-aligned 3rd rail in many cities around the world, fun fact

[@tompao7832]

Many? Not really...

[@Mergatroid]

Watching this as a Chicagoan I didn't realize how unusual it is that Chicago has an entirely uncovered top contact third rail for the entirety of the 'L' , which even includes a lot of grade crossings on the Brown, Purple, Pink and Yellow lines.

[@sonicboy678]

Speaking of the Yellow Line, that was converted to third rail.

[@TootlinGeoff]

The rail network of the whole of South East England, roughly speaking south of the Thames and as far west as Bournemouth uses uncovered third rail. There are plenty of level crossings and remarkably few accidents due to electrocution. Trains on the main line from London to Southampton run at speeds up to 90mph, unusual for a third rail system.

[@TonyP9279]

I noticed that; also noticed workers crossing those tracks. The train has to stop and wait for them to clear the tracks.

[@grassytramtracks]

@@TootlinGeoff the third rail goes all the way to Weymouth

[@TootlinGeoff]

@@grassytramtracks Thx I wasn't sure about the stretch west of Bournmouth. I knew when they electrified the SW mainline, they initially stopped at Bournmouth and put a diesel on to pull the 4TC sets to Weymouth.

[@WhoIsChristianGoldman]

This is a wonderful explanation, thanks! I see a pantograph in action every day and still think it's an amazing bit of engineering and infrastructure that goes mostly unnoticed.

[@haisheauspforte1632]

The Hamburg S Bahn also has a branch where the trains run on the regular DB network with overhead wire with the rest od the system being equipped with side contact third rail

[@jan-lukas]

Here in cologne the Stadtbahn uses 750/800V overhead wire, and what that enables is that some parts of the tracks are shared with freight trains as overhead wire is the standard on nearly all tracks in Germany. Only thing that had to be done was changing the voltage when the new lines were opened

[@misterspike]

Thank you for defining catenary and pantograph! Your lay viewers appreciate it!

[@imsbvs]

Great shot of that Eurostar train passing through Stratford International Station (I was there last week to see the same for myself!!) That's going from London to Paris or Brussels. The centre (island) platform serves domestic "High Speed" services, the outer platforms are not used so much but are available for when required eg London 2012 Olympics. These High Speed trains use overhead power lines when on the faster lines and 3rd rail power track on the traditional railway routes, with swap overs whilst stopped at Ashford or Ebbsfleet stations (depending on route in service). The changeover takes seconds to complete and passengers don't notice a thing - except the change in speed of travel afterwards (of course). (Similar to Thamslink trains as you mentioned). As for weather, a few years ago when there an exceptionally cold and snowy snap in Southern England there were massive problems with freezing rain and ice on the 3rd rails, indeeed one train broke down due to power supply flactuations damaging the onboard electrics, and I got stranded for over an hour due to loss of power. (Near Ramsgate in Kent).

[@jesse4202]

Thank you Mr Transit for this video

[@adem9599]

Fun fact: London's old trams used to use a hybrid system (3rd rail and overhead) you can still see the remains of the 3rd rail in the kingsway tram tunnel

[@davidstone408]

There is an example of how this worked I believe at the London Transport Museum Depot - which is open a certain times of the year

[@cieludbjrg4706]

London and Washington DC used "conduit" in the city centre since overhead wires were considered "unsightly". A few top contact systems had been tried, but none worked properly or safely enough. Since then, Alstom has developed its "APS", Alimentasion Par Sol (or something like that), using a top contact third rail that is divided into sections that are only energized when a tram is over it (them). It works well in milder climates, in Oslo where we have frost and snow and a highway department very much in love with salt, and in Bergen where they occasionally get bad frost (being a very exposed coastal city), not much so. Bordeaux solved the problem of "no overhead wires in the city centre!!!" with batteries.

[@cieludbjrg4706]

BTW: Oslo’s metro used to have cars operating on catenary on one half of the system and third rail ob the other half of the system. Long story short, the "west" was comprised of old suburban lines using 1-2 cars, with conductors and level crossings and overhead wires, the east was (for the most) built as a "proper" metro using 2-6 cars, ticket sales in staffed stations and third rail. The systems were totally separate until the 90’s, when the two city tunnels were connected. Gradually, the lines on the west were converted to "pure" metro, and the overhead replaced with third rail. The dual cars ran in 3-cars-formation, as that was the longest platforms on the west in "pre-metro" time (platforms were extended from 2 to 3 cars). Finally, the last line to go was the one to Holmenkollen & Frognerseteren. But it only runs with 3-cars sets of the new MX class cars, and the rearmost, or third car is closed since the platforms only accomodate 2 car trains. But since the MX sets are open throughout, it works out. Twio stations can take 6 car trains, Holmenkollen and Frognerseteren. On "Holmenkollen day" express trains are run from city centre to Majorstuen to Holmenkollen. Now, it’s surprisingly snowy in Holmenkollen (that’s probably why they built that huge ski jump there…) and that makes for problems for the third rail subway cars. They have difficulties getting the snow cleared from underneath the third rail, and when enough snow collects on the shoes, the trains stop. They are working on it, of course, but on bad days, the service is replaced by mini buses (the roads there being too small for regular buses). And the MX cars don’t have sand, which gives problems when the leaves fall. Some lines are badly affected by this, but they try to spray a sort of gel that gives a better grip on the track. Which works reasonably well. In London, they spray away the leaves with high pressure water. Leaves (and grass) on the tracks becomes almost like soap, and the tracks get horribly slippery. The trams use sand to counteract this, the subway has done totally away with sand for safety reasons (sand can insulate a train from the track circuit, making it "disappear", which means the section will show up as "clear" despite there actually being a train there, and for maintenance reasons, no sand means clean ballast, able to do what it’s supposed to do. However, the subway cars got track brakes on the middle cars of each set after a few episodes when the anti-slip/skid protection practically had trains lose their brakes. RM Transit has an episode on the Oslo Metro. It’s VERY condensed, so pay attention! :)

[@miguelsojo3376]

In Spain rigid catenary is also used on new mainline urban tunnels, even for high speed lines, although obviously they run at not more than 100/120 kmh. A good example is the newly opened (1/07/2022) Chamartin-Atocha-Torrejon de Velasco HSL, wich on its urban underground section runs with rigid catenary. It is said that for this kind of underground low speed infrastructure, it has lower maintenance and installation costs, and it also occupies very little space.

[@seanC3i]

You missed one of the best examples of a train system that uses both overhead wiring and third rail on the same service: The New Haven Line of Metro North Railroad, which serves New York City and its Northern suburbs including into Connecticut. Running from Grand Central Terminal in New York City, the New Haven Line uses third rail power at 700V DC to just outside NYC at Pelham, NY, where it switches to overhead line at 12.5kV AC. Just a few miles further at New Rochelle, NY, the line becomes shared with Amtrak long distance services joining it from a line from Penn Station to the South, which also use AC overhead electricity - Metro North and Amtrak services share the rest of the line from New Rochelle NY to New Haven, Connecticut using said overhead line all the way.

[@keegaroo6577]

Hey! I enjoyed the previous version of this video and I'm happy to see a revamp of it! Do you have a video/could you please make one explaining different rail types and terminology? (eg. regional rail, commuter, light rail, etc)

[@ads086]

The Sydney light rail operates both the Alstom third rail and also overhead, it changes modes at Town Hall station. There's also a light rail in Newcastle (Aus) that I think operates by battery, and charges via overheads as it stops at each station.

[@mdhazeldine]

Great video. Kudos for mentioning mentioning the UK southern rail network (you need to make a video on that a some point!) and Thameslink. Thameslink is interesting because it also uses rigid catenary in the central section around Farringdon/Blackfriars. One question your video threw up for me is WHY the Underground uses a 4 rail system when 3 rails works perfectly fine for everyone else. After a quick search on Google, apparently it's because the isolated traction current return allowed a train's position to be detected using DC track circuits (which I think can now be done with 3rd rail systems but couldn't back when the Underground was first electrified), and reduced any earth leakage currents that could affect service pipes, telephone cables, or cast iron tunnel liners.

[@_aidid]

This electric rail system has been interesting me since my childhood, and your video has given me the essential information to understand its work procedures

[@kwlkid85]

There are also some diesel trains fitted with pantographs/shoes so they can run on electric power on portions of their routes. This is becoming pretty popular in the UK with new trains like the class 755, 800, 802 and 88. Also there's the class 768/769 which were converted from electric only trains into tri-mode diesel, 3rd rail and OHL trains.

[@kwlkid85]

The class 768 is a really interesting train not only for it's tri-mode power but also because they've been converted from passenger to freight trains.

[@mrvwbug4423]

In New York both LIRR and Metro North have dual mode diesel and 3rd rail locomotives. It allowed them to run express trains from their diesel served network all the way into Penn Station, since they use the same cars as NJT which are double decker but built specifically to fit the loading gauge for the NYC commuter rail tunnels.

[@donberg01]

The reason why the London's Underground rail system has four rails is for stray current return. This fourth rail mitigates the problem of electrolosis due to the fact the stray electrical current will corrode nearby steel pipes and structures. The fourth rail has a low impedance return current path back to the power source, or generator. This keeps all metal structures in the vicinity from rusting.This also aids in tripping the circuit breakers faster because of higher currents, all to prevent electrical shocks.

[@cieludbjrg4706]

There were a few cities in USA that were so worried about stray currents that their trams were totally insulated and used two wires, like trolley buses. :)

[@pedroasmribeiro]

Here in São Paulo we are using rigid catenary for the newer greenfield metro Lines (4, 5 and under construction 6 - probably). The older metro lines (1, 2 and 3) use 750 V DC third rail.

[@oforid2227]

i saw in your video about double decker buses that you went to Richmond so thank you for that i hope you enjoyed it :) there is also little village (kind of) called Ham and also Petersham you could visit if you haven't already it is inbetween Richmond & KIngston P.s. and also if you want to know some history about it then i'm happy to tell you about it

[@theelectricwalrus]

So I'm assuming that dual mode catenary third/rail works decently well since the AC from the catenary needs to be rectified into DC anyway before the motor controller reconverts into 3-phase AC at the right frequency for the speed the train is currently at So putting the third rail DC at the same voltage as the output of the rectifier means that the only additional equipment you need is a third rail shoe

[@davidty2006]

The Class 373's were just that. They had 3rd rail pickups ontop of the pantograph so they can access waterloo.

[@jonathanj8303]

Quite a lot of systems do exactly that, particularlyfor multi-voltage stock that can operate on 20 and/or 25kV AC, and 3000v / 1500v DC (Usually also overhead). The only serious limitation is that because the DC-bus voltage has to match the DC supply option, that can limit overall power to whatever the maximum DC current is, particularly for a 600v or 750v system.. With modern power electronics, that often just means a reduction in output when operating on 3rd rail or DC overhead, with full power only available on AC overhead.

[@RMTransit]

I'm loving the rather technical discussion going on here!

[@mancubwwa]

@@jonathanj8303 Ok I'm not that good at super technical details, but you can circumvent the power output limitation. I.E. Pendolino family trains can operate at their top speed of 250 km/h at both 3kV DC, 15 kV 16.7 Hz AC and 25 kV 50Hz AC. And while 250 km/h is generally considered the limit for 3 kV DC system that is more of a limitation of substations and catenary than trains themselves.

[@jonathanj8303]

@@mancubwwa All power supplies have an upper limit for the current they can supply. It can be down to the wires/3rd rail, ie IsquaredR losses, or it can be further limited by substations. And part of the reason for the latter is that medium voltage DC is less efficient than high voltage AC, so you need more substations for it, and closer together. Obviously, for any given current limit, 3000v DC can supply twice the power that 1500V can, and 4x 750V, that's just maths. So 3000V is more capable and suitable for higher speeds and heavier loads than 1500V, but not as good as 20kv or more. The other factor in this is that having a 1500V or 3000V DC bus maybe on the low side, particularly for a modern high power loco. It can force you into using higher current (bigger, heavier, more expensive) IGBT's when you might otherwise be able to design a lighter, cheaper and more efficient loco if you had a higher bus voltage and lower currents. In the end, building an AC/DC machine is a compromise, but the nature of where the different supply systems are used generally means that usually isn't an issue in operation. 3kV might be good enough (just) for the pendolino to run at 250km/h, but not any faster. FS has to completely replace all their original E404 300km/h power cars, because although they were mechanically fine at 300km/h they drew too much current. All 30 sets got a pair of new dual-voltage (25kV AC/ 3kV DC) power cars when they were less than 15years old, and only then did the trains run in regular service at 300km/h. (The original DC units were refurbished and formed into 'new' sets with older coaches to run lower speed services on classic lines.) A long time ago, the USSR, which had large mileages of 3kV DC, tried building an experimental 6kV set-up (the loco was based on a VL8, I think, that tells you how old it was), but it never got beyond testing. Presumably the efficiency and output gains weren't enough to compensate for the extra problems, at least with the technology of the time.

[@ErebusNT1]

And my personal favourite is Detroit's trams that are overhead wire + battery to power them during a couple of sections with no overhead wires.

[@hypernewlapse]

A lot of systems use this in europe (Bordeaux, Sevilla, Zaragoza…) either with batteries, supercapacitators (like a battery that doesn’t degrade but can’t carry the voltage for lots of times) or a strange third rail that only activates when the tram is on top (APS)

[@cooltwittertag]

sad how it was cut short by nimbys and lack of initiative by the city

[@mr51406]

Excellent overview. To a La Presse columnist who superciliously complained that the wiring of the REM on the Champlain bridge was “visual pollution,” I’d say I’d be much much, more worried about the gaseous, respiratory pollution generated by all the SUV’s and “light” trucks on the bridge.

[@grassytramtracks]

This is just the sort of NIMBYism I have very little patience for

[@Hogtownboy1]

This is your most nerdy video yet. I love it

[@hypernewlapse]

Overhead wire for everything and supercapacitators for tram sections in historic city centers (like Caf technology in Sevilla and Zaragoza or Alstom in other places).

[@elroysterckx242]

The Rotterdam metro combines both. It is third rail in the city center and overhead wires on converted rail lines into the suburbs.

[@James_Knott]

The old streetcar system in Washington D.C. used a 3rd rail, which was below ground between the rails.

[@drearyplane8259]

As someone from the South of the UK, I will say third-rail is nice for being visually unobtrusive, single and double tracks can blend into the countryside very easily.

[@shriramvenu]

i fell the overhead wires blend into the countryside just fine too. In fact windmills fit the country side nicely as well. It's all a matter of perspective. Modernity can sit perfectly in harmony with nature

[@mrvwbug4423]

Yep, it's how LIRR in New York manages to be quite unobtrusive for what is the busiest commuter rail system in North America. They can squeeze em into some pretty tight ROW. It's common to see LIRR ROW running in what would be alley space between the back sides of houses in most places in the US.

[@jarjarbinks6018]

It would be cool to see Seattle raise its platforms and use overhead wire powered heavy rail like Cleveland used for its red line

[@crzwdjk]

Surprisingly, there have been some new grade crossings with third rail built in Europe, or rather lines with grade crossings that got converted to third rail. Oslo's Line 1 was an interurban style line with overhead wire and grade crossings but it got converted to metro standard third rail, keeping the crossing. And in Rotterdam, the metro line to the Hague was converted from a mainline railway, mostly keeping the overhead electrification but the third rail does extend across one grade crossing on the Rotterdam end.

[@cieludbjrg4706]

There was no way to avoid the grade crossings (without either building huge road bridges or lowering the track). It was after all a low-cost conversion. The other lines on the west (2, 3, & 4) were completely metrofied with new under/overpasses for crossing roads, some even being completely closed (such as by Egne Hjem on the Kolsås line). The line to Bergkrystallen opened as "premetro" in 1957 with trams, and became the first full metro line in 1966. The line to Oppsal (extended to Bøler in 1958, Skullerud in 1967 and finally to Mortensrud in 19xx (20xx?) opened as a suburban tram line in 1926 to Oppsal, extended as premetro to Bøler in 1958, and gradually converted to metro during the 50s and 60s by building stations, removing grade crossings (replacing them with over/underpasses) and some changes in alignment to get better gradients and curves. The other two lines on the east (Grorud, now Vestli) and Furuset (now Ellingsrudåsen) were full metro from their opening in 1966-67, and never saw pre-metro operation with trams.

[@NotReallySan]

hey rm, please do a video about the belgian railway, i'd apprieciate it

[@keacoq]

Increasing voltage is more important than the choice of AC or DC. And higher voltages are more practical with AC because of simpler switching and transformation, although modern electronics is changing that. Trains mostly use 25kV single phase AC, which can be difficult to take from three phase distribution systems, especially where the train loads are large compared with other loads on the system. It is possible to use three phase power by using two catenary wires and the rails. One very old example of this is La Rhune in SW France.

[@meongmeong3599]

the problem with 3 phase electrification is, it is very difficult when Catenary entering junctions. For small railway station it maybe not a big problem, but when entering city station, it's much more complicated than dc overhead or ac single phase, and it's one of the reasons Italian railway stop using it

[@keacoq]

@@meongmeong3599 Single phase electrification places large single phase loads on the power supply network, so three phase might help with that. But it is non-standard, complicated at junctions as you say, and difficult in confined spaces like tunnels. Where was it used in Italy?

[@meongmeong3599]

@@keacoq it's their standard from early 1900s, until 1970s. Mostly Northern Italy, southern Italy was electrified later with 3 kV DC, but 3 kV DC became standard to replace 3 phase systems in northern part

[@newfelo]

In Santiago Metro, new lines 3 and 6 use rigid catenary at 750VCC and National Railway (EFE) commuter, regional and national lines use 3KVCC double catenary just like in Italy

[@vjaska]

Not only Thameslink but also Overground & Southern services to Watford switch between overhead and third rail when crossing through London - in fact, the Overground does it on three different parts of the network

[@fetchstixRHD]

Also Southeastern High Speed services, and Great Northern Moorgate services!

[@gabrielstravels]

Such concept that happens in the UK also happens in Athens (Greece) too on Metro Line 3, where trains going to the airport switch between third rail and overhead (same voltage as the UK too!)

[@RealCadde]

It's good that you finally mentioned third rail for trams, because i assumed you would have missed it completely. Also referred to as Ground-level Power Supply. I just want to add that many tram systems used to have third rails in the early days, as far back as the 1880's. They all had their issues and some were insanely unsafe. One in particular, Stud Contact System, suffered from a design flaw that make the electrical contacts that were flush to the ground to always be live. Meaning any unsuspecting thing passing over it and closing the circuit would be hit with significant juice. Another was a system that was always live, but buried into the ground with a "plow" that would make contact with the electrified rail. The principle was that since the live rail was buried, anyone passing over it would be safe. But of course it didn't work too well because random garbage would make its way into the slit and destroy the "plow" or get jammed between the contact point and rail. And anything that could conduct electricity, such as a strip of metal, could get in there and provide a protruding live feed that would make fireworks happen to anything touching it. And then there's the issue with snow, ice, and especially salty water which would electrify the surface... Third rail for street level trams/light rail simply doesn't make much sense.

[@cieludbjrg4706]

The stud system was energized when trams passed over, by magnetism from the tram. However, the studs "jammed" with power on, thus zapping unsuspecting horses. The conduit system worked reasonably well in London (but it was very labor intensive, a man (…) had to manually insert a shoe in the track when a tram came, and take care of the ones that came off trams when they passed out of that section. I’ve heard somewhere that DC quit its trams system after a bad freeze stopped the entire system, which, like London, used conduit in the city centre. The French APS actually works, but I wouldn’t mix that with salt or snow & ice…

[@treinspotterlarssie]

In the netherlands we always had the sneltram (intercity tram) Overground it only stopped at bigger stations and used a pantograph And underground it would turn into a metro and use 3rd rail

[@pegasustargaryen]

The S Bahn Hamburg (Germany) uses 1200V DC third rail, but on the S3 extension to Stade the train switches to overhead wire power at Neugraben station.

[@meongmeong3599]

Hamburg S Bahn is interesting. First built with High Voltage AC 6600V, then converted to third rail DC 1200V. Do you know some technical reasons about why this is happen? I cannot find a reasons why, at least from English literature

[@davideddy5877]

Very interesting video sir.

[@MervynPartin]

Further to your mention of the lower profile in tunnels with 3rd. rail, where tunnel boring machines are used, in order to get the clearance for overhead catenary, there is a massive increase in the amount of ground spoil that has to be removed because the tunnel width is also increased, so to me, the use of 3rd. rail cuts construction costs considerably. Where existing lines are electrified, low bridges and tunnels do not need rebuilding., although here I would mention the South Wales Metro, currently under construction. I believe that the intention is for the tram-trains to use battery power in some locations, not only on the proposed street extension in Cardiff Bay, but also through the Caerphilly tunnel where the catenary will be grounded due to the low clearance and water ingress from the tunnel roof. The first Stadler tram-trains have arrived at the new Taffs Well Depot and are being line tested. I would be interested to see your take on the system in due course.

[@ulysseslee9541]

Rigid Catenary also extensively use in new Underground tracks in Hong Kong's MTR network, Starting from West Island Line extension for Island Line when it launch service in 2015. The Latest, East Rail Line new track from Hung Hom to Admiralty is in full Rigid Catenary.

[@AnykeyNomad]

Sofia, Bulgaria - M3 line also uses "rigid catenary" in tunnels, and a classic wire at the open section (near and at depo).

[@efaber3565]

For the TTC subway, it is called the Traction Power. As the for light rail transit is called Overhead Contact System.

[@chrismckellar9350]

What Reece forgot to mention, is the new generation of passenger trains being the hydrogen fuel/battery urban metro, regional and inter-regional trains like the Alstom Coradia iLint which has been in commercial services in Europe for 5 years, the Stadler Wink, Stadler GTW and Siemens Mireo Plus H. Alstom has launched for France's SNCF regional rail services. the Alstom Coradia Polyvalent H2 being 4 carriage 218 seat electric and hydrogen fuel/battery regional and inter-regional passenger rail services.

[@stephenreardon2698]

Merseyrail in the UK has introduced hybrid third rail/battery trains so it can extend it service on to neighbouring none electrified lines. Testing has proven very positive so far, not only to new stations under construction on the edge of the system, but out far enough to connect to other parts of the UK rail system, where it could connect to the overhead line system at places such as Preston & Wigan to recharge the batteries. Battery powered trains do feel a little gadget bahn at the moment as the technology is yet to settle on a set of suitable solutions, but that surely deserves a video in itself, as many of the worlds more rural providers, and those where neither overhead nor third rail seem appropriate, are looking into this option

[@mrvwbug4423]

Honestly battery or fuel cell trains don't make sense. You're adding maintenance items, a potential safety risk with large numbers of lithium batteries, and reducing the trains efficiency as it now has to carry its energy source with it just like a diesel, though probably less efficient than a diesel. It's almost certainly cheaper in the long run to electrify the line, as it allows for a lighter, cheaper train with less maintenance required and you remove the risk of having lithium batteries, hydrogen tanks or diesel tanks on board the train.

[@chrismckellar9350]

@@mrvwbug4423 - Hmm. Alstom Coradia ilint hydrogen fuel cell/battery trains has been in operating in Europe since 2018 without any major incident's. Also France's national rail operator SCNF is introducing the Alstom Coradia Polyvalent H2 being a 4 carriage electric/fuel cell/battery for France's regional passenger rail network. Alstom has licence their electric/fuel cell/battery technology to Spanish rolling stock manufacturer CAF (Construcciones y Auxiliar de Ferrocarriles).

[@GhostVGO]

In the southern part of england the timetable is actually designed with the third rail gaps in mind, there are certain locations trains cannot stop and more than x trains an hour cannot pass through incase of delays, for instance GTR Southern 4 car units cannot use certain platforms because of the gap in the third rails

[@richardhuss]

And then (long ago) there was the Giant's Causeway Tramway in Northern Ireland, built as a third rail roadside tramway. Later mercifully converted to overhead.

[@cieludbjrg4706]

It was, after all, a very early electrification. :) There is still a French mountain line (!) that for/to a large extent still uses third rail (!).

[@grassytramtracks]

@@cieludbjrg4706 The UK still uses third rail on a lot of railways (most lines south of London) and even some fairly long routes such as London to Weymouth (which I would bet is the Longest single 3rd rail powered line in the world)

[@Bioshyn]

There are parts of the Autobahn A5 and A1 modified into a test track for electrified trucks with overhead wires.

[@manankaushik4966]

In Delhi metro, there is an overhead third rail supported by the cantilevers when the train runs underground ie in the tunnels

[@texassswain1664]

Great stuff ...think there is a tram system in southern France that uses battery power,being recharged at stops,, modern maintenance trains on subways are battery powered, so future trams, local trains services have the potential to do away third/overhead rails, so safer overall and less maintenance

[@grassytramtracks]

I know that one of the lines on the Nice tramway does that

[@WoomiestWoomy]

I’ve always thought overhead wires are really pretty

[@matthewschilling1289]

Cough... Ties .....Cough ..... Great video!

[@phs125]

Some things to say about indian stuff. In metro systems, we have either a 750V third rail DC, or 25kV overhead AC, And for railway, they use overhead only, so probably 25kV AC. But until last decade, most of railway was still being run on diesel engines. And in my childhood, in early 2000s, they were still being referred to as steam engines,(a regional word for "train") which is probably just old language. The only big city I've been to is Bengaluru. They have a metro system which runs on 750V DC third rail. But the newly proposed Suburban railway will apparently run on 25kV overhead, even though half of the tracks will be elevated. (Just like almost all of metro is elevated) Also. Most of indian railway tracks are broad gauge. But Bengaluru metro is standard gauge. But suburban railway will be broad gauge. In my early childhood, all metre gauge tracks were converted to broad gauge.

[@denelson83]

Do not forget the class 395's in the UK, which operate on both 25kV AC OHLE and 750V DC third rail.

[@mikeythesoulace]

British Rail Class 395 Javelins like what you've shown in your video do still run at somewhat high speed (less than 230 km/h) but still have third rail capability

[@markusstudeli2997]

Thank you for this very easy to understand explanation of different electrification systems! In the context of electrification, could you tell us something about the legendary "crocodile" locomotive model you have on display in your background?

[@justcomments335]

Informative vid as usual. Would you ever consider doing a whole video on Alstom APS? I'd love to hear your opinion on it as I can't really see the point.

[@LeGrandJuju49]

The point is to counter opposition against tram catenary in front of historic sites, could it be from institutions or common NIMBYs. There is no other reason Bordeaux accepted to develop this as far as I know.

[@justcomments335]

@@LeGrandJuju49 Yeah, I get that, but I just don't understand what it is some people find so obtrusive about catenary wires, and when you consider how unreliable APS is, I just don't see how it can be worth it.

[@LeGrandJuju49]

@@justcomments335 Compared to having nothing wires are obtrusive, that's why in France we buried electrical wire in cities in the 2000s to begin with.... APS has a reliability over 96% since 2006 so this argument is no longer really relevant even if I think this is less than catenary. installing APS still costs 10 to 20% more than catenary. But this is a costs cities are willing to commit to, because expensive transit is better than no transit, especially since the aesthetics of public transit are an integral part of the urban fabric and experience often for at least the next 50 years after construction. In France, use of APS is a great tool to circumvent authorities having veto power to protect historical monument, which mayors always have problem with. For example, this kind of opposition caused the T3a and T3b common termini at Porte de Vincennes to be so bad by forcing the old tram arrangement of the late 19th century instead of a contiguous 4 track station...

[@ravenmusic6392]

In the UK we have a really odd system where the south of the UK almost entirely uses 3rd rail and the north uses 25 kv overhead, and I mean mainline commuter trains, not just subways. Like so many London stations are electrical hazards cause they have both 3rd rail and overhead lol, some even have 3rd rail platforms, 4th rail for the tube and 25 kz for trains going north

[@barrieshepherd7694]

Typo it's 25kV . There are no unprotected electrical hazards the engineers fully understand the issues and engineer the installations to cater for all the differences. The 4th rail on dual National Rail / TfL tracks (e.g. Euston to Watford) is actually at the same 0 potential as the return rail unlike when in TfL land where it's above the running rail potential. Thus TfL stock can run on NR track but NR stock cannot run on TfL 4 rail track.

[@kjh23gk]

Thanks to you I've just realised why, in the first Mission Impossible film, they based it on the UK leg of the Eurostar route for an action scene: it has third rail instead of catenary. 😃 If only they had used a model of the TGV TMST instead of the TGV Atlantique.

[@TheGreatPOD]

Great video, one type you didn't mention was overhead power from a pole as opposed to a pantograph. In San Francisco we have vintage street cars that run up market Street that use a single pole to take power and return power through the steel rails that the train runs on. There is a second wire which is used as a return for rubber wheel trolley buses running on the same right of way. It's an interesting case study of having two different vehicle types running using the same power. Not sure if there's any other systems in the world that share power between a steel wheel on steel rail street car and trolley buses on rubber tires, although I wouldn't be surprised if there's someplace in Europe that does that. Keep the great videos coming, thanks

[@kericlapboards7737]

Seattle also has streetcars and trolleybuses, but the streetcars use pantographs. Both use 750V DC.

[@cieludbjrg4706]

I believe it was the wear and tear of the trolley wheel that in part hastened the changeover to pantographs. Trolley buses use "skids" with carbon insets, but trams used a little wheel. Some interurban lines used to change the trolley wheel at the end of the line for every run. The pole leaving the wire in high speeds will be more detrimental to the train than a bit of slack on the overhead. But, the last great interurban in America, the North Shore Line, ran fast trains, and then passed thru streets like a tram before joining the subway cars (using third rail) on the Loop in Chicago. The Great Southern still has trains running thru the streets in some town, but they are planning on rerouting the line outside them (since motorists tend to be idiots & play "chicken" with the trains). However, they have long since converted to regular pantographs. I think (think) trolley poles are unsuitable for very high speeds (and possibly voltages). Blackpool had overhead suitable for both, since their vintage trams used poles. I’ve heard rumors Brussels is also dual operable. Toronto is getting rid of their poles. San Francisco uses poles on the Market Street line, where the vintage trams run, but elsewhere, it is pantographs.

[@TonyP9279]

I don't think it's the same power. If I recall, the Market Street street car has it's own overhead over the rails which is located in the leftmost lane of Embarcadero, for example. The buses were confined to the outer-most lanes and had their own pair of overheads which were tied together with insulating spacers to maintain separation, especially around a turn. One thing I have always wondered about those trolley buses, is that sometimes one of those poles does come off the wire, like when the bus deviate too far off in order to get around the street parking, so that pole is "floating" electrically. If the other pole is attached to the hot side of the circuit, you have a live voltage swinging around. This is assuming there's not a safety on those things. I'm not sure which line is hot or neutral (grounded)

[@francisrogers9824]

There are some tram systems in the classic era, like London, which used a third rail conduit despite running on street levem

[@samuelringrose2955]

Can you please talk about the Prague transport system? I'm from Prague and even though the transport is incredible, it doesn't get any attention. Please make a video about it.

[@durece100]

The New Haven Line from Metro North has both third rail and overhead wires.

[@RazielKainus]

in Vienna you have a couple electric busses which run on battery, but if they need charging, they can do that with raising a pantograph towards tram overhead wires :D ... I believe there is like one line that uses those there :)

[@d1234as]

If there is enough room, overhead line is always the best choice. Rigid catenary is the best choice for tunnels, expecially for those ones that doesn't have enough space for catenary overhead and are long enough to don't have huge seasonal and/or daily termal excursion. Third rail should be relegate for tunnels without sufficient room to any type of overhead line, neither catenary nor rigid.

[@cieludbjrg4706]

The Madrid Metro uses overhead, since third rail tends to be in the way…

[@PoshManSweets]

I'm a Driver Trainer for Thameslink (and Great Northern), so get to experience both AC & DC. Personally AC is better, if you're going Rapid Transit. You just get more power on tap from the 25kv AC than the 750v DC. The Difference is so noticeable from the Cab... Rigid Catenary works well for lower tunnels etc. AC is more pricey overall.

[@middletransport]

Depends. Places such as Hong Kong or Tokyo use a higher voltage of DC at 1500v

[@pwhnckexstflajizdryvombqug9042]

In Sydney they use 1500v DC too and they double strung the wires so trains can pull more amps. It's still less than the power you can get out of 25kv AC but it's as good as you're going to get without completely redoing it all.

[@joshlikescola]

A lot of the south eastern services in the UK are starting to hit the limits of what is possible on 3rd rail electrification, just because of the sheer number of services being run. It has been vaguely floated that the 3rd rail will be replaced by OLE at some point in the future, which seems likely. Fortunately, the fact that dual mode units are so prevalent helps considerably if we decide to do it more gradually, such as for electrification in many places. (Funnily enough, diesel/electric bi-modes seem to actually result in more electrification, rather than an excuse to avoid it)

[@malcolmmccaskill2311]

Why not add batteries to the trains? In Melbourne new trams required substantial upgrades of the DC overhead electrification, but the following contract was to include batteries on the trams rather than upgrade the overhead power supply. The high current draw is only for a few seconds when starting from a station.

[@gpsimracing579]

The best solution I've seen for me are the Nice trams. Running on traditional overhead lines connected to buildings, but relying on a battery in places where catenary poles would have been disrupting to the historic sights.

[@rileycummaudo8612]

Newcastle’s light rail also uses a different method of electrification by having charging stations at the light rail stops

[@pav3_08]

I am Italian and I live near Milan. Milan metro, as you said in the dedicated video is split up. The metro line 1 or the red line M1 uses DC third/fourth rail while green line M2 and yellow line M3 use overhead wires. I suppose M4 and M5 run on third rail since I never saw an overhead wire but it's difficult to see anything like that due to the platform screen doors. I found out that all the metro trains in operation are actually supplied with both third rail capting systems but also with a pantograph, making every equipment movable between lines. I saw it in person where a M2 train transited down at M1 station "Precotto" where a maintenance facility is located, supposedly for maintenance works. Our trains, especially the S lines use overhead wires but on the station of Pavia on the S13 line, for a slight moment the overhead wires stop and then come back at the station itself (terminus). I suppose there's a third rail under the train because it doesn't have any loss of power. Fun fact, during June this year, a thunderstorm broke down most of the overhead wires for trams and trolleybusses, pointing out how brittle things can be. Another example is from "Via dei Missaglia" where trams 3 and 15 run, a car hit a overhead wire tension pole and deviated the 2 lines for 3 weeks.

[@evanzinner6589]

Reese, MBTA in Boston is looking at electrifying the commuter rail. They’ve recently said that they plan to roll out overhead catenary most places, but will be using batteries to bridge the gap where putting in catenary would be very difficult (under bridges, tunnels, etc.). What are your thoughts on a system like this? Are there any systems like this in the world? Do battery electric trains still have a lot of the benefits of traditional electric trains? I’d love if you could have a video on this, but a reply would be cool too

[@cieludbjrg4706]

I think that can work out well. Battery-electric trams (and trolley buses) are already in operation.

[@KenyonKarl]

Decades ago, the Chicago 'L' (CTA/CRT) had far more mileage at ground level than it has now: (Douglas Park (Pink), Ravenswood (Brown), Skokie (Yellow) and Evanston (Purple) Evanston, Skokie, Lake Street (Green) used trolley wire power, while Ravenswood, Garfield (Blue), and Douglas used third rail. Furthermore the lng forgotten Chicago Aurora & Elgin Railway used third rail for most of its service to the Fox River Valley cities that it served, using trolley wire only in its Wheaton Yard, railroad interchanges, and the Fox River city terminals. Third rail is ALMOST universally 600 volts DC, although one Michigan interurban used 1200 volts DC. Also Bay Area Rapid Transit uses 1000 volt third rail. Most of the long forgotten interurban railroads used 600 volt DC trolley wire in spite of the rather long distances involved and the use of rotary converters to convert power from AC to DC (before rectifiers were technologically feasible). Thus the interurban from Chicago to Milwaukee required a substation every EIGHT miles to power their many heavyweight six car trains. Conversely the Indiana Railroad got by with substations every 15 miles as trains were short, lightweight, and less frequent. Light Rail Vehicles, old-fashioned streetcars and trolley buses universally use 600 volts DC power. But many other voltage and AC/DC arrangements can vary widely for suburban and intercity electrifications.

[@cieludbjrg4706]

The standard now is 750 V for both. Oslo’s third rail metro used 750 V from the start, the tram network changed over around the year 2000.

[@fredblonder7850]

You should have mentioned the Conduit System used by the Washington, DC Streetcars. This is basically a third and fourth rail UNDERGROUND.

[@rmschindler144]

if I ever encounter you (say, if you visit Crema in West Van), and it comes together that I receive the privilege of your company, I think I’d really enjoy sounding the mind of somebody possibly even more obsessive about great design than I am.

[@lzh4950]

12:04 Actually its speculated that the future Cross Island Line in Singapore's MRT will be using overhead wires/rails again, like the older North East Line (which Siemens has won a contract to replace its wires (that have loosened in the past, causing service disruptions) with rails), likely as higher voltages could be safely allowed, which is more important as power transmission losses will become more significant given the ~5km distance between stations when the line crosses beneath the Central Catchment Nature forest Reserve The Bt Panjang LRT in the same country also uses 600V AC instead of DC despite the short distance between stations (~500m), which has been blamed for making its power system less reliable as it apparently has to use, as a result, a more complicated design that's harder to maintain (the current collector shoes have 8 contact points with the power (& also guide) rail which sometimes break off)

[@laju]

One thing with the choice between AC and DC is the need of on board transformer with an AC system, which tend to be heavy. Sometimes the weight is a good thing, for example heavy electric locomotives, which need the weight to have enough adhesion. On the other hand, light rail systems benefit from being... well, light.

[@MarioFanGamer659]

That's interesing and explains the question I never asked, why trams use DC instead of AC.

[@apk55]

The amount of power you can get on low voltage DC systems is limited to about 2MW because the currents get so massive. OK UK Southern region has stretched this to 4MW in parts of the network at the expense of substation little over a mile apart and trains which automatically only take this power on known section. Do not forget that 4MW at 750V is over 5000A requiring massive cables. With these high currents there is considerable voltage drop resulting in the system often being rather inefficient. Even my local Tramway network (Manchester Metrolink) has had problems with voltage drop and recently had to put in some new substations at for example Brooklands because of voltage drop problems. In contrast high voltage AC systems can easily deliver train loads of 10MW or more, which is required for heavy freight or fast passenger trains

[@monishbiswas1966]

Do overhead lines ever use DC? There is HVDC used for power transmission so could this be adapted for trains?

[@apk55]

@@monishbiswas1966 The high voltage DC used in power transmission lines is way too high for railway applications, being hundred of KV and requiring clearance of meters. Even with 3KV designing equipment cases is a problem as clearances start becoming large typically 50 mm. While 6KV DC systems have been proposed it would be a problem designing compact equipment cases for mounting on multiple unit trains. In contrast with AC the only high voltage parts is the transformer primary which is normally submerged in an oil bath with high dielectric strength.

[@grassytramtracks]

And in some areas the 3rd rail system is struggling. On services from London Waterloo to Weymouth, the 2 5 car units have to decouple at Bournemouth because the electricity west of there can't handle 10 carriage trains

[@RazielKainus]

UK Javelins also have the overhead wire / third rail capabilities :)

[@pwhnckexstflajizdryvombqug9042]

You can put air gaps in overhead wires, the wires on each side of a level crossing rise up above the max height and the pantograph disconnects for the gap where there is no wire. The only thing you have to make sure to do is open the main breaker to stop arching and make sure all of the trains on the network have pantographs with the same maximum height. It is normally done on freight railways where huge mining vehicles and trucks need to be able to cross the rail tracks.

[@barrieshepherd7694]

Most UK main line OLE installations use insulated 'wire' gaps, an air cap would cause the pantograph to shoot up and then tear down the next section of OLE. The train detects magnets (same as fixed AWS magnets) which are located on the sleeper ends to close the traction down so that the field in the on-train transformer is quenched so when it joins the new section it can connect without a potential 'bang'.

[@pwhnckexstflajizdryvombqug9042]

Yes I think all systems that use 25kv have to have insulated gaps, however what I was talking about is air gaps so that over height loads can cross the railway tracks. there are some videos of them on KZbin, presumably you would have to design the pantograph with it in mind.

[@pwhnckexstflajizdryvombqug9042]

25kV Air Gap: Australian Railways if you want to see what I am talking about.

[@Jestersage]

I wonder if you will ever do PRT, especially Morgantown. Since you seems to be a lot more knowledgeable in public transit then many others.

[@andrewcox6863]

I understand why the 1st REM line is overhead (it used an at grade overhead electrified line) but I would question why the 2nd REM line and Toronto Relief line is overhead, although snow might be the reason.

[@LeGrandJuju49]

Although rubber tyred metros use two guide rails which double as power rails, both are positively charged and sometimes only one is used in depots and low speed conditions. The closest guide rail to the platform at stations is isolated and made out of epoxy resin to be safer for passengers in Paris at least. VAL system is the exception, where one guide rail acts as neutral and the other one is 750 V DC powered.

[@cieludbjrg4706]

In Paris, the guide rail(s) are 750 V DC+, and return is via copper brushes to the running rails (steel rails) in the middle of the track. The steel rails also operate the track circuits. Works trains (converted from old steel wheel Métro stock) can thus run on the "Pneu" lines without problems, they just need an extra side-mounted pic-up shoe.

[@ironlynx9512]

Another example of switching electrification as the service changes: Line B of the Rotterdam Metro: At its eastern end, it runs on a newly built light rail alignment, powered using overhead equipment due to a lot of level crossings. The light rail alignment allows for speeds of maximally around 70 kph. In its centre, it runs on third rail and largely underground, allowing speeds up to 80 k, assuming the vehicles can accelerate enough before the next stop. On the western side of the network, it follows a decommissioned heavy rail line where they hooked up light rail power to the old mainline catenary. Speeds climb to 100 k, thanks to wider stop spacing.

[@ironlynx9512]

The Rotterdam Metro has a few lines that do something fun. Perhaps that could be one for a future video?

[@RMTransit]

@@ironlynx9512 Yes! If you are actually in Rotterdam and could help please do reach out!

[@ironlynx9512]

@@RMTransit Sadly I'm not, so you might have to try hitting up someone closer to the city...

[@zackgro8440]

good video

[@williamerazo3921]

Yes a re do. I will also go 3 rd rail

[@SomeGuy-lw2po]

The South Eastern Javalin train are also a duel voltage (OLE and 3rd) highspeed train no?

[@reinerjung1613]

Hamburg has also new trains that can use third rail in the old network and a pentograph on normal train line.

[@RMTransit]

Hamburg is yet another city I really need to cover haha