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Developing Passenger Car Unit (PCU) at Signalized Intersection in Context of Bangladesh

Md. Monirul Islam1*, Soumik Nafis Sadeek1, Jobair Miah2, Forhad Hossain2
1Department of Civil Engineering, IUBAT-International University of Business Agriculture and Technology, Dhaka, Bangladesh
1Faculty and 2Student
*Corresponding author: E-mail:

ABSTRACT: Passenger Car Unit (PCU) is an important metric to measure traffic load in transportation system. PCU measures the impact of different transport modes on traffic variables compared to passenger car. It converts the heterogeneous traffic into homogeneous traffic condition. PCU, itself is dynamic in nature, so, it changes in regular basis depending on road environment and traffic condition. PCU varies country to country and even within the country. Developed countries have sufficient research on determining PCU for their own highways, but developing countries like Bangladesh has extreme laggings in determining PCU for its built roadways. So, this research contributes to estimate PCU at signalized intersections based on traffic speed and volume using multiple linear regression model. Our results suggested PCU values of motorbike, autos, buses and trucks, which give different results compared to Highway Capacity Manual (HCM). In some cases, motorbikes possess PCU more than 2.0 which indicates its ample influence of creating traffic anomaly at intersections. Also, bus possesses PCU more than 6.0 which indicates large queue and illegal maneuver of heavy vehicles while entering or exiting into an intersection.

KEYWORDS: Passenger Car Unit, Passenger Car Unit, Multiple linear regression method, Signalized intersections, Speed, Volume

Passenger Car Unit (PCU) is a metric that is used to assess traffic-flow rate on highway or expressway or freeway. PCU is a measurement that evaluates the impact of different modes of transport i.e., heterogeneous traffic on different traffic variables e.g., headway, speed, density or occupancy compared to single passenger car. The logic of PCU actually lies in to convert mixed traffic into a homogeneous traffic stream assuming that only cars are travelling on a road (Cao et al., 2010). Various confounding factors; environment, weather condition, time of the day etc, significantly effect on traffic flow parameters and therefore, PCU depends closely on these parameters (Ahmed, 2009). The main importance of PCU is its ability to convert a mixed traffic flow into homogeneous and to derive different traffic characteristics, for example, capacity analysis, saturation flow rate, traffic stream model, etc. (Prasetijo, 2007). Moreover, road environments vary among different countries. So, a country-wise PCU estimation is of necessity for transportation planning purpose. Consequently, PCU determination would help the policymakers and transport authorities to develop road safety standards for developing countries like Bangladesh.