Passenger Car Equivalents for Basic Freeway Segments on Addis Ababa – Adama Expressway
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Date
2016-05
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Addis Ababa University
Abstract
In freeway traffic flow contains different types of vehicles, due to the variation of vehicles in the
traffic flow the speed of passenger cars influenced by heavy vehicles, for the reason that heavy
vehicles uses more driving area of the road and limited performance. Hence according to local
conditions developing Passenger Car Equivalents (PCE) for trucks and buses on upgrade and down
grade is an essential parameter. So the major objective of this research is to evaluate Passenger Car
Equivalents (PCE) for trucks and buses for basic freeway segments on Addis Ababa – Adama
Expressway and compared with that of Highway Capacity Manual 2010 provided.
The data was collected from the field by using videotaping on Addis Ababa – Adama expressway in
the selected sites on the basic freeway segments at every collection site for the percent grade with
the corresponding grade length. And the development of Passenger Car Equivalent was carried out
by transcribing the recorded video in to tabular form with proportion of trucks and buses, base flow
rate and mixed flow rate and also analyzed by using Equal Flow Density method.
In this study the proportion of trucks and buses considered from 10% up to 50%, the Passenger Car
Equivalent increases as the proportion of trucks and buses decreases. The major variation observed
in lower trucks and buses proportion non-linearly because the interaction between trucks and buses
with passenger cars increases. Moreover for trucks and buses proportions from 10 % up to 50 %,
the value of PCE varies in between 1.4 up to 7.8 for upgrade up to 5 % which is higher than the
HCM 2010 recommended value that varies between 1.5 up to 3.0. For trucks and buses proportions
of 10 %, the value of PCE varies with the length of grade in between 5.6 up to 7.8 for 5 % upgrade
which is higher than the HCM 2010 recommended value that varies between 1.5 up to 3.0.
The study concludes that while analyzing by using the executed Passenger Car Equivalents shows a
better assumption than Passenger Car Equivalents on HCM 2010. So the executed Passenger car
Equivalents for the basic freeway segment on Addis Ababa – Adama Expressway provides a
realistic result while analyzing the traffic flow.
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Road and Transport Engineering