Why the City of Nashua Switched from Line of Sight Preemption to Glance

[@SuperRicky511]

Love this insight into NFD. Their response times always amaze me, whether I’m listening to my scanner or recalling times I’ve needed their help. NFD is a top-tier department that truly exemplifies professionalism.

[@danlowe8684]

I've worked on the design, inspection, maintenance, troubleshooting, repair, and construction of over 1000 traffic signal systems during my 36-year career and have yet to encounter any of the Opticom problems mentioned in this video. Line of sight issues are easily addressed during the design and installation phases. I have probably replaced a total of 10 detectors and a couple of discrimination cards in my career and have never had an emitter go bad. Of all the traffic-related products I have worked with, Opticom is likely the most robust and trouble-free component. It is very cost effective, too. Disclaimer: I have absolutely no ties to, nor financial interests in Opticom or any other traffic related products.

[@tonyp9179]

Why can't cities get light timing right?

[@danlowe8684]

@@tonyp9179 If you could give me a bit more info, I could probably answer more coherently...

[@danlowe8684]

@@tonyp9179 OK, likely because they have a fire department guy that knows nothing about signals, and a city traffic guy, that was painting crosswalks last week, but today is being asked about signal timing, chiming in on the subject. Both have been promised larger OT budgets if they agree to say things about Opticom that are not true.

[@tonyp9179]

@@danlowe8684 are there any performance standards?

[@danlowe8684]

@@tonyp9179 The goal is to get as many vehicles through an intersection, every hour, as possible. So, we perform 'turning movement counts'. This is where, along a commuter route, traffic techs physically count how many cars enter a given intersection, at any given hour, on any given day, and which direction they enter and which direction they go. This data is inputted into a traffic software program (my favorite was called 'Synchro', developed by Texas U). This then runs a simulation and gives cycle lengths (max time to service all 8 phases), offsets (distance between coordinated intersections along a given corridor), and splits (% of time allotted to all 8 phases of traffic movements) - cycle, offset, split = COS. This timing is then loaded into all local (intersection) controllers and coordinated by a master controller (master monitors and coordinates all local controllers along a corridor). Then, this timing is observed in the field by techs and adjustments are made. The biggest problem is that most major metro commuter routes are over-saturated - meaning that more vehicles are present than can be possibly run through the intersections. This is where longer cycle lengths are used, because the yellow and all-red times burn up seconds every cycle. So, when you are stuck at a red light on a cross street to a major highway during the day, it is because the master is trying to get platoons of cars through the corridor. It will then allow the cross street to join the platoon and sync up the progression once again. Things like pedestrians (which are guaranteed time) and emergency vehicle preemption interfere with this progression. Now, in the middle of the night, the same intersections should snap right to the cross-street vehicle that approaches because it is likely running 'free', with no need for progression. But one thing I always told the public that called to complain about signal timing is that 99% of the time they were correct, and a detector was hanging up, a pedestrian button was malfunctioning, etc., that caused a problem. Commuters that drive a route every day notice changes and should not hesitate to call the road authority to complain. There are alarms set in the controllers to alert the techs to a problem but are sometimes missed. I hope this helps. Let me know if you have any other questions.

[@BobRiebe]

Extremely innovative city making their citizens safety a big priority utilizing the most innovative technology available ultimately saving lives.

[@TheDarkpagan88]

But.. Does AMR (contract city ambulance) and surrounding towns that go to the 2 ers in town have a way to activate the systems

[@proteanwanderer]

AMR doesn’t have it (yet.) To my knowledge, neither do any of the other services from surrounding towns. On the other hand, the law is perfectly clear: pull to the side and come to a complete stop. If the world were perfect, people would have gotten this memo years ago.

[@danlowe8684]

Another issue that is not mentioned in the video is the fact that no EVP system can pre-empt out of a pedestrian clearance phase in signal controllers. In other words, the 'flashing don't-walk' (ped clearance) mode must be allowed to finish before an EVP call is allowed to be serviced. In busy downtown areas with a lot of foot traffic, this can appear as a malfunction to the emergency vehicle operator when, in reality, it is a safety feature mandated to allow pedestrians to clear the crosswalk with no changes in timing parameters.

[@BobFrTube]

This isa great argument to use a generic packet infrastructure rather than being the accidental properties of a particulate brittle technology such as cellular.

[@wiz_techno6656]

damn over here in the Boston area we're lucky IF there's even an opticom installed on the light 💀

[@margaretsmyth1564]

Nashua is huge city getting plenty of taxes

[@08jk74x]

It’s just tax dollars.

[@Teeveepicksures]

What do YOU think tax dollars should go toward? More tax breaks for the wealthy?

[@goldbrick2563]

The enormous tax expenditure for this is definitely worth it

[@MrTaco6]

well if they didnt do this and then you're in a car accident in Nashua and the FD is 10min late than they should've been, you can bleed out in comfort knowing the town saved a few dollars.

[@jaypee902]

Preemption is a luxury-the vast majority of fire districts in the United States have no preemption capability, and they somehow make it to the scene in a timely manner.

[@proteanwanderer]

I couldn’t agree more. We need to trim things back to what’s reasonable and affordable. For that matter, if we got rid of seatbelts and airbags, backup cameras, and that kind of thing, think of how many people would be able to afford a car? The vast majority of people drive carefully every day, mile after mile, never needing their safety equipment in their entire lifetimes.

[@Ryan-hi6zg]

2nd biggest FD in New Hampshire, but yet you still have master boxes. Get with the times ffs.

[@Hammy16]

Master box will always be faster than a monitoring company. I can have my firefighters out the door by the time the monitoring company calls. 40 years ago you had 17 minutes to get out, now you have 3-4. Every second counts.

[@Ryan-hi6zg]

@ I’m assuming you’re a firefighter since you have no clue what you’re talking about. There is no need for master boxes anymore, it’s considered a waste of resource. If you want the signal to come directly to the station then just get everyone to install a radio box like an AES( Fire department has the authority to demand that) Look at Manchester, they are starting to fine people who don’t get rid of their master boxes. Also 3-4 minutes to get out? Even in a 13D home you would have more than 3-4 minutes to get out and that’s only common areas with heads. A correctly designed and installed fire sprinkler system will takeout/contain the fire 100% of the time.