Vol 8, No 5 (2017) > Civil Engineering >

Estimation of Equivalency Units for Vehicle Types under Mixed Traffic Conditions: Multiple Non-Linear Regression Approach

srikanth seelam, Arpan Mehar

 

Abstract: The accuracy of measured traffic flow on a roadway largely depends on the correctness of the PCU factors used for converting traffic counts. PCU is the number of passenger cars that are displaced by a single heavy vehicle of a particular type under prevailing roadway, traffic and control conditions. The aim of the present study is to develop more appropriate models for estimating the equivalency units of different vehicle types on multilane highways, considering the limitations of available methods. Estimation of equivalency units for vehicle types is described by developing speed models based on multiple non-linear regression approaches. The equivalency units estimated by using models are found to be realistic and logical under heterogeneous traffic flow conditions. The PCU values estimated by the multiple non-linear regression method are compared with and found to be relatively higher values than the values obtained by the dynamic PCU. The accuracy of the models is checked by comparing the observed values of speed with estimated speeds. The multiple non-linear regression approach is also used for estimating the equivalency units on six-lane divided highways. Results indicate that the proposed methodology can be used for estimation of equivalency units for vehicle types under mixed traffic conditions.
Keywords: Equivalency units; Multiple non-linear regression; PCU; Speed

Full PDF Download

References


Arasan, V.T., Arkatkar, S.S., 2010. Micro-simulation Study of Effect of Volume and Road Width on PCU of Vehicles under Heterogeneous Traffic. Journal of Transportation Engineering, Volume 136(12), pp. 1110–1119

Cao, N.Y., Sano, K., 2012. Estimating Capacity and Motorcycle Equivalent Units on Urban Roads in Hanoi, Vietnam. Journal of Transportation Engineering, Volume 138(6), pp. 776–785

Chandra, S., Kumar, U., 2003. Effect of Lane Width on Capacity under Mixed Traffic Conditions in India. Journal of Transportation Engineering, Volume 129(2), pp. 155–160

Chandra, S., Zala, L.B., Kumar, V., 1997. Comparing the Methods of Passenger Car Unit Estimation. Journal of Institution of Engineer, Volume 78, pp. 13–16

Chandra, S., Kumar, V., Sikdar, P.K., 1995. Dynamic PCU and Estimation of Capacity of Urban Roads. Indian Highways, Volume 23(4), pp. 17–28

Cunagin, W.D., Messer, C.J., 1982. Passenger Car Equivalents for Rural Highways. Transportation Research Record, No. 905, pp. 61–68

Huber, M.J., 1982. Estimation of Passenger-car Equivalents of Trucks in Traffic Stream. Transportation Research Record, No. 869, pp. 60–70

IRC 64, 1990. Guidelines for Capacity of Roads in Rural Areas. Indian Road Congress, New Delhi, India

Karim, M.R., Anand S., Sekhar, S.V.C., 1999. Development of Passenger Car Unit (PCU) Values for Malaysia. Journal of the Eastern Asia Society for Transportation Studies, Volume 3(3), pp. 73–80

St. John, A.D., Kobett, D.R., 1978. Grade Effects on Traffic Flow Stability and Capacity. Technical Report NCHRP Report 185, Washington, DC

Transportation Research Board, 1965. Special Report 87. Highway Capacity Manual, Washington, DC