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 Capacity and LOS: Example Problems

 
Heavy Vehicle Adjustment Factor

A six lane freeway has a flow of 3500 vehicles. This flow consists of 180 trucks per hour, 200 RVs per hour, 350 passenger buses per hour and the remainder of passenger. Calculate the heavy vehicle adjustment factor for a ½ mile section of this freeway that has a +4% grade.

 

[Solution Shown Below]

 

 

 

 

 

 

 

 

 

 

Solution

The percentage of trucks is 5% [(180/3500) x 100], buses is 10% [(350/3500) x 100] and RVs is 6%. The heavy vehicle adjustment factor is calculated using the following equation:

fhv=1/(1+Pt*(Et-1)+Pr(Er-1))

ET =passenger-car equivalents for trucks and/or buses = 3.0 (see applicable adjustment table)
ER = passenger-car equivalents for recreational vehicles = 2.0 (see applicable adjustment table)
PT, = proportion of trucks/buses in the traffic stream = 5 + 10 = 15%.
PR = proportion of RVs in the traffic stream = 6%

Therefore,
                     fhv=1/(1+0.15*(3-1)+0.06*(2-1))
                                = 0.74