Through Traffic Passenger Car Equivalents for Selected Signalized Intersections in Addis Ababa, Ethiopia
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Date
2019-05
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Addis Ababa University
Abstract
Currently, there are about 34 registered signalized intersections in Addis Ababa. As most
of developing countries the capacity and level of service for these facilities is measured
using manuals adopted from overseas. Among the overseas manuals the Highway Capacity
Manual (HCM 2010) is the most common one. Different vehicle types occupy different
spaces on the road, move at different speeds, and start at different accelerations.To adress
such differences HCM(2010) has a conversion to saturation flow rate of signalized
intersections in units of passenger cars per hour per lane (pc/h/ln). Currently, a PCE value
of 2.0 is specified for all through heavy vehicles where no distinction is made between
trucks, recreational vehicles, buses and other vehicles in the calculation of the adjusted
saturation flow rate at signalized intersections.
Traffic and drivers behavior in other countries may be significantly different from the
situation in Addis Ababa, Ethiopia. Developing local values will minimize the errors we
incur at every step of our capacity analysis due to the use of adopted manual input
parameters. In this study the researcher has developed local through traffic passenger car
equivalents for small busses, large busses, trucks and truck trailers on selected signalized
intersections of Addis Ababa with significant number of heavy vehicles. Using drone
technology as a data collection tool and deploying the headway ratio method for
determining through traffic PCEs the researcher has come up with new local values. The
study showed that the mean local PCEs of Small Busses are 1.49, 1.51, and 1.68 on first
(inner), second (middle), and third (outer) lanes respectively. Similarly the mean local
PCEs of Large Busses are 1.95, 2.20, and 1.99 on first (inner), second (middle), and third
(outer) lanes respectively. Trucks on the other hand have mean local PCE values of 1.62,
1.56, and 1.44 on first (inner), second (middle), and third (outer) lanes respectively.
Whereas, Truck Trailers have larger mean local PCE values which are 3.62 and 3.78 on
second (middle) and third (outer) lanes respectively. Moreover, on relatively level
approaches the PCEs are larger than the PCE values on down and upgrades. While, lane
width has low effect on PCEs, approach width has significant effect on PCEs. Similarly,
the available green time has direct relationship with the PCE values.
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Keywords
Passenger Car Equivalents, Saturation Flow Rate, Signalized Intersections, Headways