Abstract
In this paper, empirical research about Passenger Car Equivalents (PCEs) on the longitudinal downgrade of two-lane roads in Bosnia and Herzegovina has been conducted in order to determine the influence of vehicle structure under free traffic flow conditions. The research has been carried out considering the classes of vehicles at cross-sections on the downgrade of two-lane roads. As a result, the negative influence of vehicle structure under free traffic flow conditions using passenger car equivalents (PCEs) has been determined. The results show that on the downgrade of two-lane roads, the value of passenger car equivalent decreases from the level terrain to the boundary minimum value for the determined downgrade g = −3.00%, after which its value starts to increase slightly. Based on the obtained values, the models calibrated with a second-degree polynomial have been developed to determine the average value of passenger car equivalent as a function of its boundary value. The paper also compares the results obtained by the developed models with the models from the Highway Capacity Manual under free traffic flow conditions. In addition, models for the percentage values of PCE15%, PCE50% and PCE85% have been established.
Highlights
Passenger Car Equivalent (PCE) is used exclusively to convert a heterogeneous traffic flow into an equivalent homogeneous flow composed solely of passenger cars
By analysing PCE values on the downgrade of two-lane roads, the highest correlation coefficient is for auto trains (AT), while the lowest value is obtained for all light vehicles (LV), which is below 0.5
The results obtained as a result of valid empirical research confirm the starting hypothesis of the paper that PCE values on the downgrade of two-lane roads are in complex functional dependence on the flow structure, driving and dynamic characteristics of vehicles and drivers, and especially on technical and exploitation characteristics of the roads
Summary
Passenger Car Equivalent (PCE) is used exclusively to convert a heterogeneous traffic flow into an equivalent homogeneous flow composed solely of passenger cars. The calculation of equivalents is important for determining the capacity and level of service on the roads, since inclusion of these values provides a relevant indicator of the impact of commercial vehicles (CV) on road infrastructure. The category of commercial vehicles (light vehicles, heavy-duty vehicles, buses and auto trains) includes all motor vehicles, which do not belong to the class of passenger cars according to their physical driving and dynamic characteristics in the conditions of road network operation. Commercial vehicles occupy more space than passenger cars, and driving and dynamic characteristics of these vehicle classes are less favourable compared to the class of passenger cars. The problem arises in the analyses, i.e. the application of the HCM (Highway Capacity Manual) in local conditions, where the impact of commercial vehicles on the roads, i.e. PCE, is underestimated or overestimated due to the saturation of certain road sections
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