NCEES Transpo Prob 523

[NICKOLI]

The answer key for the NCEES references an example from the Garber & Hoel book (P.520) for the equation to calculate total trips per household. The problem is the Garber & Hoel book uses a factor of 0.82 but the NCEES solution shows a factor of 0.58.

Depending on which factor you use, you either get answer A or C even though it says the answer is A based on the NCEES solution.

Anyone run across this?

 

[lady_j]

I worked the problem, and got the correct answer. ... what I did was just "plug" the values into the given equation....I didn't have to use anything to look up an equation because it was given.

For everybody, here's the question:

"A multiple regression analysis for trip generation purposes shows the following relationship for the number of trips per household:

trips generated per household per day = .58 + 1.5P + 2.2A

where:

P= number of persons per household

A = number of autos per household

if a zone under study contains 600 households with an average of 4.1 persons and 2.3 autos for each household, the number of trips generated per day is most nearly:

a) 7,100

b 6,700

c) 6,600

d) 6,200

*The answer I got was "a", actual answer 7,074.

 

[civilized_naah]

The answer key for the NCEES references an example from the Garber & Hoel book (P.520) for the equation to calculate total trips per household. The problem is the Garber & Hoel book uses a factor of 0.82 but the NCEES solution shows a factor of 0.58.
Depending on which factor you use, you either get answer A or C even though it says the answer is A based on the NCEES solution.

Anyone run across this?

The 0.58, 1.5 and 2.2 are simply regression parameters from a best-fit analysis for a particular region. In the G&H example, a different model (based on a different data set) was specified. There is nothing universal about either one. Coming up with these coeffcients is a huge exercise, so the only questions they can really expect you do in less than 5 minutes is this plug and chug variety. Just use the model the question specifies.

 

[IlPadrino]

Depending on which factor you use, you either get answer A or C even though it says the answer is A based on the NCEES solution.

Never... and I do mean NEVER... make a problem harder than it needs to be. If they give you an equation, use it! Drawing a pretty picture to prove Pythagorean's most famous theorem won't get you any bonus points. And the danger, of course, is making assumptions that weren't used in the construct of the question and answers.