Calculating Vp

[maximus808]

While doing some of the examples in the Chelapati books, I came across a problem than asked for the passenger car equivalent flowrate or Vp.

Is it possible to calculate this without being given a % of Trucks or Rvs? Is there an assumption we can make if this is not given as it is part of the equation Vp=V/[(PHF)(N)(fhv)(fp)]. They also made an assumption for PHF being 0.90. Is there a time when we can make this assumption for certain scenarios. Thanks.

 

[civilized_naah]

While doing some of the examples in the Chelapati books, I came across a problem than asked for the passenger car equivalent flowrate or Vp.
Is it possible to calculate this without being given a % of Trucks or Rvs? Is there an assumption we can make if this is not given as it is part of the equation Vp=V/[(PHF)(N)(fhv)(fp)]. They also made an assumption for PHF being 0.90. Is there a time when we can make this assumption for certain scenarios. Thanks.

The heavy vehicle factor WILL require input about terrain and %trucks, %RVs etc

If these values (fp, fHV, PHF) are not given, look in the HCM for default values. For example, Chapter 23 deals with analysis methodology for freeway segments, but an earlier chapter (maybe 12, I don't recall) has definitions etc related to Freeway segments. The earlier chapter defines defaults values for variables, if any are defined.

 

[Civil02]

Default values of parameters:

Freeway:

if the field mesuared data not available, following default values may be used.

LW = 12 ft

LC= 10 ft

BFFS = 75 MPH (rural), 70 mph (urban)

PHF = 0.88 (rural), 0.92 (urban)

% of HV = 10 (rural), 5 (urban)

DPF = 1 for weekdays , 0.85 for weekend in recreational area

Multilane Highway:

LW = 12 ft

LC= 6 ft

BFFS = 60 MPH

APD = 8/Mile ®, 16/M (Suburban), 25/M (Urban)

PHF = 0.88 (rural), 0.92 (urban)

% of HV = 10 (rural), 5 (urban)

DPF = 1 for weekdays , 0.85 for weekend in recreational area

 

[maximus808]

Civil02, thanks! Where'd you find these default values? Thanks again

 

[Civil02]

From a book " all in one civil engineering pe" by Goswami. very good book for pe exam.

 

[maximus808]

I just got it, thanks. The Trans section is a lot better than the CERM

 

[Ambrug20]

I just got it, thanks. The Trans section is a lot better than the CERM

You also may find default values in HCM p. 9-9, 10-17

 

[maximus808]

I didn't check but are they the same as the all in one pe guide