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 Capacity and LOS: Example Problems

 
Calculating Flow Rate

A four-lane highway (two lanes in each direction) has a 2,500-vph peak-hour volume that includes mostly commuter traffic, 5% trucks and 6% buses. The section of highway that we are interested in is in rolling terrain. The peak-hour factor has been determined by earlier studies to be 0.95. What is the passenger-car equivalent (or service) flow rate for this section of freeway?

[Solution Shown Below]

 

 

 

 

 

 

 

 

 

 

Solution

The equation for calculating the passenger-car equivalent flow rate is:

vp=V/(PHF*n*fhv*fp)

V = peak hour volume (vph) = 2,500
PHF = peak-hour factor = 0.95
fHV = heavy-vehicle adjustment factor =

1/(1+Pt*(Et-1)+Pr*(Er-1))=1/(1+(0.05+0.06)*(3-1)+0(2-1))=0.82

(for ET and ER, use the small table for extended general freeway segments)
fp = driver population factor = 1.0 for commuter traffic
vp = 15-minute passenger-car equivalent flow rate (pcphpl)

2500/(0.95*2*0.82*1)=1605