lindeburg sample exam errors

[gcj]

anybody else finding errors while checking why your answers were wrong?

so far, i think i've found 2 errors in the pm transportation section of sample exam:

#168 - they subtract 300 twice. shouldn't it only be once since the table says to use 150 for 2 lanes? are we supposed to assume since there are 2 lanes, that we need to subtract 2/3L twice from the pc?

#170 - rv's are not included in the calc for fhv, but should be since it states in the HCM that you could disregard the percentage of rv's only if the ratio of trucks/buses to rv's is greater than 5:1

if i am wrong, please let me know.

thanks!

 

[petobe]

anybody else finding errors while checking why your answers were wrong?so far, i think i've found 2 errors in the pm transportation section of sample exam:

#168 - they subtract 300 twice. shouldn't it only be once since the table says to use 150 for 2 lanes? are we supposed to assume since there are 2 lanes, that we need to subtract 2/3L twice from the pc?

#170 - rv's are not included in the calc for fhv, but should be since it states in the HCM that you could disregard the percentage of rv's only if the ratio of trucks/buses to rv's is greater than 5:1

if i am wrong, please let me know.

thanks!

#168 - Did you mean #167?

If so - the subtraction of 300 twice is correct. It represents two different things... the first being the superelevation runoff, and the second being the tangent runout. The 150' presented in the table is 1/3 of the superelevation runoff - you know this because it says "runoff in the curve"... The "in the curve" part is the key. 1/3 of the superelevation runoff occurs in the curve, while the other 2/3 occurs prior to the PC.

Secondly, it says that the tangent runout is twice the value in the table - so another 300'. So the beginning of the superelevation transition is just as it is presented in the solution (PC-2/3L-Tr)

#170

The percentage of RVs are included... Trucks + buses + RV = 26% (they used .26 in the solution as the percent trucks) Be careful on your interpretation of what the HCM is saying in regard to the percentage of RVs... It doesn't say that you can disregard them if the ratio is 5:1, it says that you can include them with trucks if the ratio is 5:1 - which is what they did in this solution (See HCM p23-8, 3rd paragraph)

 

[gcj]

#168 - Did you mean #167?
If so - the subtraction of 300 twice is correct. It represents two different things... the first being the superelevation runoff, and the second being the tangent runout. The 150' presented in the table is 1/3 of the superelevation runoff - you know this because it says "runoff in the curve"... The "in the curve" part is the key. 1/3 of the superelevation runoff occurs in the curve, while the other 2/3 occurs prior to the PC.

Secondly, it says that the tangent runout is twice the value in the table - so another 300'. So the beginning of the superelevation transition is just as it is presented in the solution (PC-2/3L-Tr)

#170

The percentage of RVs are included... Trucks + buses + RV = 26% (they used .26 in the solution as the percent trucks) Be careful on your interpretation of what the HCM is saying in regard to the percentage of RVs... It doesn't say that you can disregard them if the ratio is 5:1, it says that you can include them with trucks if the ratio is 5:1 - which is what they did in this solution (See HCM p23-8, 3rd paragraph)

i thought i might b wrong. i think my brain needs a nap. hopefully that doesn't happen during the exam :\

i'll look over these probs again. thanks!

 

[gp08]

are these the only errors you've found? I'm having a hard time with problems 121-124. If the add both N and E to find the PT coordinates, why would they subtract E when finding the PC coordinates. Aren't they both east of the PI?

 

[petobe]

are these the only errors you've found? I'm having a hard time with problems 121-124. If the add both N and E to find the PT coordinates, why would they subtract E when finding the PC coordinates. Aren't they both east of the PI?

#'s 121-124 are structural problems in the Lindeburg Sample Exam I have (2nd edition)... so i am not sure.