Volume List  / Volume 6 (4)



DOI: 10.7708/ijtte.2016.6(4).08

6 / 4 / 453-473 Pages


Preethi Prathapan - Department of Civil Engineering, College of Engineering, Trivandrum, India -

Ashalatha Rajamma - Department of Civil Engineering, Government College of Engineering, Kannur, India -


Estimation of saturation flow under heterogeneous traffic condition is a challenging task in the capacity analysis of signalised intersections due to complexity of vehicular interaction. Studies have established that quantification of vehicular interaction can be achieved by estimating Passenger Car Unit (PCU) values for different categories of vehicles in the traffic stream. Most of the studies have used ratio between speed differential and horizontal projected area of vehicles to model dynamic PCU. At signalised intersections speed ratio would not vary much and hence these models do not capture the exact dynamic nature of PCU in its full extent. In this study dynamic PCU for heterogeneous traffic at signalised intersections is estimated based on area occupancy, an indirect measure of extent of road usage. Traffic flow details at the intersection area during saturated green time are collected from different signalised intersections to determine the area occupancy of the heterogeneous traffic. The field determined area occupancy and mean occupancy time are utilized to determine the equivalent homogeneous traffic stream area and the number of standard car spaces (NCS) existing in the traffic stream. The individual PCU values are estimated based on NCS and number of various categories of vehicles existing in the traffic stream during saturated green time. The PCU values estimated indicate that traffic characteristics, control conditions and approach width have significant effect on PCU values and the effect is predominant in the PCU values for heavy vehicles. The PCU values of vehicles passing through signalised intersections with the control condition through and right turn movement permitted in same phase are lower than the PCU values of vehicles passing through intersections having through only movement in one phase.

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The authors would like to acknowledge the Kerala State Council for Science, Technology and Environment (KSCSTE),Government of Kerala, India for financing this study.


Aggarwal, P. 2011. Passenger Car Unit Value for Trucks using Fuzzy Model. In Proceedings of the World Congress on Engineering,  II, 1017-1020.


Al-Kaisy, A.; Jung, Y.; Rakha, H.2005. Developing passenger car equivalency factors for heavy vehicles during congestion, Journal of transportation engineering, 131(7): 514-523.


Arasan, V.T.; Dhivya, G. 2010. Methodology for determination of concentration of heterogeneous traffic, Journal of Transportation Systems Engineering and Information Technology, 10(4): 50-61.


Arasan,V.T.; Jagadeesh, K. 1995. Effect of heterogeneity of traffic on delay at signalized intersections, Journal of Transportation Engineering, 121(5): 397-404.


Arasan,V.T.; Vedagiri, P. 2006. Estimation of saturation flow of heterogeneous traffic using computer simulation. In Proceedings of the 20th European Conference on Modelling and Simulation, 393-398.


Arkatkar, S.S.; Arasan, V.T. 2010. Effect of gradient and its length on performance of vehicles under heterogeneous traffic conditions,  Journal of Transportation Engineering, 136(12): 1120-1136.


Basu, D.; Maitra, R.S.; Maitra, B. 2006. Modelling passenger car equivalency at an urban mid-block using stream speed as a measure of equivalence, European Transport, 34(2006): 75–87.


Benekohal, R.F.; Zhao,W. 2000. Delay-based Passenger Car Equivalents for Trucks at Signalised Intersections, Journal of Transportation Research Part A, 34(6): 437-457.


Bhattacharya, P.G.; Mandal, A.G. 1980. Investigation of passenger car equivalents at controlled intersection in Calcutta, Highway Research Bulletin, 14: 41-64.


Chandra, S.; Kumar, U. 2003. Effect of lane width on capacity under mixed traffic conditions in India, Journal of Transportation Engineering, 129(2): 155-160.


Chandra, S.; Molla, D. 2010. Change in Vehicular Interaction and Saturation Flow at Signalized Intersections over Time, Highway Research Journal, 3(1): 69-76.


Chandra, S.; Sikdar, P.K.; Kumar, V. 1996. Capacity analysis of signalised intersections, Highway Research Bulletin, 54: 129-152.


De Luca, M.;  Dell'Acqua, G. 2014. Calibrating the passenger car equivalent on Italian two line highways: a case study, Transport, 29(4): 449-456.


Dhamaniya, A.; Chandra, S. 2010. Concept of stream equivalency factor for heterogeneous traffic on urban arterial roads, Journal of Transportation Engineering, 139(11): 1117-1123.


HCM. 1965. Highway Capacity Manual- HCM Special Report, 87, Transportation Research Board, National Research Council, Washington, DC.


HCM. 2010. Highway Capacity Manual- HCM - Special Report, 209, Transportation Research Board, National Research Council, Washington, DC.


IRC. 1990. Guidelines for capacity of urban roads in plain areas. Indian code of practice. IRC: 106-1990.


Keller, E.L.; Saklas, J.G. 1984. Passenger car equivalents from network simulation, Journal of Transportation Engineering, 110(4), pp.397-411.


Lee, T.C.; Polak, J.W.; Bell, M.G.H; Wigan, M.R. 2010. The Passenger Car Unit Values of Motorcycles at the Beginning of a Green Period and in a Saturation Flow. In Proceedings of the 12th World Conference on Transport Research, 1-17.


Maini, P.; Khan, S.K. 2000. Discharge characteristics of heterogeneous traffic at signalised intersections. In Proceedings of the 4th International Symposium on Highway Capacity, Transportation Research Circular E-C 108, 258-270.


Mallikarjuna, C.H.; Rao, R.K. 2006. Area Occupancy Characterestics of Heterogeneous traffic, Transportmetrica, 2(3) (2006): 223-236.


Mehar, A.; Chandra, S.; Velmurugan, S. 2014. Passenger car units at different levels of service for capacity analysis of multilane interurban highways in India,  Journal of Transportation Engineering, 140(1): 81-88.


Radhakrishnan, P.; Mathew, T.V. 2011. Passenger car units and saturation flow models for highly heterogeneous traffic at urban signalized intersections, Transportmetrica, 7(2): 141-162.


Rahman, M.; Nakamura, F.; Okura, I. 2003. Measuring passenger car equivalents (PCE) for large vehicles at signalised intersections, Journal of Eastern Asia Society for Transportation Studies, 5: 1223-1233.


Sumner, R.; Hill, D.; Shapiro, S. 1984. Segment passenger car equivalent values for cost allocation on urban arterial roads, Transportation Research Part A: General, 18(5/6): 399-406.


Tiwari, G.; Fazio, J.; Gaurav, S. 2007. Traffic planning for non-homogeneous traffic, Sadhana, 32(4): 309-328.


Webster, N.; Elefteriadou, L. 1999. A simulation study of truck passenger car equivalents (PCE) on basic freeway sections, Journal of Transportation Research, Part B,  33(5):323-336.