Quadratic Formula for Vertical Curve Design

[@FindleyDaniel]

Correction Notice: The final answer for the example problem is correct (1,831'), but the incremental steps show inaccurate information. When developing the problem, I must have inadvertently changed the problem but failed to update the text on the description - I apologize for any confusion this may have caused. The correct values should be as follows: 0 = 0.625L^2 - 11.75 L + 5.625 Therefore (for the quadratic formula), a = 0.625, b = 11.75, and c = 5.625

[@nazirsaleh9123]

how did you get the 150 value in the x equation ?

[@FindleyDaniel]

Nazir, this is basically just a given in the problem at around 4:05 - kzbin.info/www/bejne/api4qaJnn82oatU

[@nazirsaleh9123]

@@FindleyDaniel I have the same problem but what was given to me just the elevation of PVI and g1 ,g2 with the 300m long curve..i tried to follow your steps but seems that there many things not given to me ...so if you help i would appreciate it ...btw thanks from the Netherlands

[@FindleyDaniel]

@@nazirsaleh9123 do you have any information about where the hazard is located? Sometimes they want you to assume it's directly at the PVI or some other point.

[@nazirsaleh9123]

@@FindleyDaniel the Velourstunnel in Hengelo

[@FindleyDaniel]

@@nazirsaleh9123 I would suggest trying to locate the PVI for this tunnel and then measure the distance from the PVI to the entrance/exit that you're interested in (locate that point in relation to the distance from the PVI). Then, I assume you're trying to increase the 3.9 meter height at that point.

[@dariandekock9732]

Hi! We have found the length that the curve needs to be, but how to we find the original curve length? Thank you for this great video !!

[@FindleyDaniel]

This example was set up without an original length because we can use the generic length "L" - I've organized more videos on this topic into playlists on vertical alignment (and other topics), if it's helpful: sites.google.com/ncsu.edu/daniel-findley/educational-resources

[@footballhits7963]

Hi Sir, Thanks for your great videos. Usually AASHTO specifies Vertical clearance of 4.3 or 4.9 for roads. But vehicles does not have that much of height from ground. Why is this excess height. Is that for special vehicles such as HA/HB.

[@FindleyDaniel]

Great observation! You're right that the vast majority of vehicles do not need this much clearance (even most of the commercial trucks). The higher clearance requirement came from the Departement of Defense for the movement of military equipment: www.fhwa.dot.gov/infrastructure/50vertical.cfm

[@catgamerzxd]

I would like to know more on how the terms a, b and c equations were derived given the grades of the two tangent lines of the curve, EL of PVC and L of the curve..do you have any resources you can suggest? (My foundation includes construction the grade diagram...I would like to know/learn how to prove the equation from there)

[@FindleyDaniel]

I think I have a few more videos related to this topic in this playlist that might be useful for you: kzbin.info/aero/PLQ2tBMRKXROZsDv_W9Ax-ytgp5x3y2BQX

[@ceciliapalomo6457]

excellent example. You should have taught my class.

[@salamamohammad7276]

Thanks for your clear tutorial, but applying the same technique to metric VC didn't work. e.g : GIVEN SAG g1=-4.20%, g2=+3%, L=260 m, How to apply the formula ax^2+bx+c =Y , HOW TO CALCULATE THE "a" term ? since length in metres? Thanx

[@FindleyDaniel]

I just created a video to answer your question, I hope it helps! kzbin.info/www/bejne/gJqsqpSvoaylnsU

[@asaadhusein5063]

What type of polynomial function do they use?

[@saaizd]

Very helpful, thank you Sir!

[@amitbharmane4904]

Sir could you upload videos of traffic engineering subject

[@FindleyDaniel]

This playlist has a variety of videos on the topic: kzbin.info/www/bejne/e33dhaydf8eNj6c

[@balbirsinghsingh]

VERY EASY WAY TO SOLVE

[@kowinzhang]

how do we know the value of a, b, c in the formula?

[@FindleyDaniel]

They are based on the form of the parabolic equation (which defines the shape of the parabola, ie., how narrow or wide, how tall or short, and where it is positioned vertically). For a vertical curve specifically, a, b, and c are defined at 1:56 - kzbin.info/www/bejne/api4qaJnn82oatUm56s

[@faruktravelview6571]

thanks for helpful

[@whatdahek4120]

having a heck of a time getting the constants can anyone help please?

[@FindleyDaniel]

The final answer for the example problem is correct (1,831'), but the incremental steps show inaccurate information. When developing the problem, I must have inadvertently changed the problem but failed to update the text on the description - I apologize for any confusion this may have caused. The correct values should be as follows: 0 = 0.625L^2 - 11.75 L + 5.625 Therefore (for the quadratic formula), a = 0.625, b = 11.75, and c = 5.625

[@FindleyDaniel]

a, b, and c are defined at 1:56 - kzbin.info/www/bejne/api4qaJnn82oatUm56s