Quiz #30

[cogborn84]

Okay so I gave this problem a go last night and I solved it using the same method as most of you but for my Vp I used 2,400. If you look at the Speed v. Volume, LOS curve table for freeways, the footer of that table says that the max volume given a FFS of 70 mph (which is what I used as my S since my calculated FFS was about 71) is 2,400, so when you use 2400 as your Vp and solve for Vdemand you get 5,097 so I would have chosen 5070. what do you guys/gals think?

Using a Vp of 2,400 would put you right at capacity which would put you at LOS E. Essentially 2,400 is the base capacity of the freeway so using a vp of that is putting you right at capacity (thus LOS E). 2,401 would be LOS F. Check out exhibit 11-7 HCM and see in between step 4 and 5. Hopefully I explained that clear enough. Let me know if you have any questions about what I just said.

 

[John QPE]

You definitely don't want to use 2400 here ..... that is one car above LOS F

 

[ngmakhlo_PE]

You definitely don't want to use 2400 here ..... that is one car above LOS F

yeah as soon as I hit submit on my response I realized I used the incorrect Vp. Thank you!

 

[ngmakhlo_PE]

Using a Vp of 2,400 would put you right at capacity which would put you at LOS E. Essentially 2,400 is the base capacity of the freeway so using a vp of that is putting you right at capacity (thus LOS E). 2,401 would be LOS F. Check out exhibit 11-7 HCM and see in between step 4 and 5. Hopefully I explained that clear enough. Let me know if you have any questions about what I just said.

Yes, this makes sense, as soon as I hit submit on my answer to the question I realized immediately that I used the wrong Vp, when I originally read the problem statement I knew it was asking for Volume relating to an LOS of C but when I went home last night to solve it I forgot the LOC of C part and was just going with max capacity. Thanks for the discussion and info!! it is all helpful the closer we get to the exam!  

 

[JGipe1]

I get a solution of V = 3685 vph

View attachment 8719

This makes sense to me.

 

[John QPE]

This makes sense to me.

Bust this is saying vp, which is the demand flow rate, is 1820. This train of thought leads you to solve for S using the breakpoint equation. This flow rate would put you at LOS D on this freeway.