# Now is the time for Transportation AM



## Silvamela (Sep 5, 2008)

After my Construction question, I would like to know if anyone has found anything in CERM 11 for AM Trasportation:

1. Horizontal and Vertical Clearance

2. Acceleration and Deceleration

For the second, there is something in CERM Ch. 74, but is that it?

Thank you guys for reading this and helping. :reading:


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## vane_gator (Sep 5, 2008)

Look at Ch 78. It has small sections on both those topics. I think that entire chapter is important, though.


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## Silvamela (Sep 5, 2008)

vane_gator said:


> Look at Ch 78. It has small sections on both those topics. I think that entire chapter is important, though.


Right, Ch. 78 is important since it covers topics 1 to 4 from Tansportation AM, but not topics 5 and 6 which are those I posted above...

NCEES listed 5 and 6 under Geometric Design, but there is nothing "geometric" in Ch.74 - Vehicle Dynamics...

Yet the general opinion that all you need is CERM 11 for AM. :dunno:


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## csb (Sep 5, 2008)

If you can get your hands on a Green Book and the HCM for the test, just do it.


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## Silvamela (Sep 7, 2008)

csb said:


> If you can get your hands on a Green Book and the HCM for the test, just do it.


I went to library and looked through the Green Book 2004. I was kind of disappointed:

1. Horizontal and vertical clearance is all over the place, like in 5 different chapters

2. Acceleration and deceleration - pretty much scattered through many places too...

Another thing: LOS is not listed as topic in NCEES list but there is a problem on LOS in NCEES Sample Questions and Solutions...


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## IlPadrino (Sep 7, 2008)

csb said:


> If you can get your hands on a Green Book and the HCM for the test, just do it.


I disagree... you don't need either of those for the breadth portion of the exam. Too, it's usually not worth bringing a reference unless you're familiar with it (except for a dictionary-type reference or something that might have a qualitative answer you're looking for) - this certainly applies the the HCM or Green Book.

You should be fine with the CERM.


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## squishles10 (Sep 11, 2008)

I agree- you don't need either of those.

Here:

braking distance=(1.075v^2)/a

when distance is in feet, v is in mph, and a is the DECELERATION rate in ft per second ^2

If you're using the same standard-ish equations I have, horizontal clearance is just solving for M where M=R(1-cos(I/2)) or M=Ecos(I/2)

Vertical clearance is solve for E where E=(ALsta)/8, A=G2-G1 (always positive) and 100 ft = 1 station &lt;--- dont let that trip you up!!!

Also you should know stopping sight distances, flat and on grade, and minimum horizontal curve radius. If you don't have those, let me know.

I got all these from the Testmasters review, and I vaguely remember one question on each, none too hard though. Just be careful in the equation, lots of times the units cancel with a constant (see braking distance above).


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## Silvamela (Sep 17, 2008)

squishles10 said:


> I agree- you don't need either of those.
> Here:
> 
> braking distance=(1.075v^2)/a
> ...


Thanks so much. I am not sure I know what the minimum horizontal curve radius reffers to, if you could help a little I would much appreciate it.


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## squishles10 (Oct 8, 2008)

minimum horizontal curve refers to the radius allowed at a given speed to keep the car on the road. ie you cant make a 50 ft radius going 90 mph, but you can make a curve as big as you want as long as you have space. for the AM i think you assume the curve is flat and they give you the friction coefficient. there is an equation that will give you the radius. let me reiterate again, the trick to the AM traffic is to make sure you use the correct units!!! they may not cancel out depending on the equation you use so CHECK.


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## squishles10 (Oct 11, 2008)

use my cheat sheet on it: http://engineerboards.com/index.php?showtopic=7309


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