Ashish Dhamaniya

Concept of Stream Equivalency Factor for Heterogeneous Traffic on Urban Arterial Roads

AbstractMixed traffic flow is often converted to equivalent flow in passenger car units (PCUs) by multiplying the number of each category of vehicles in the traffic stream by their respective PCU factors and then adding them up. PCU is a complex parameter and depends on multitude of factors. This paper presents a methodology to convert a mixed traffic stream into a homogeneous equivalent without making use of PCU factors. Traffic volume and speed data collected on different six-lane urban arterial roads in India are analyzed to determine PCU values of five different categories of vehicles found on these roads. These PCU values are used to convert heterogeneous traffic volume in vehicles per hour to homogeneous volume in PCU per hour. A new term stream equivalency factor (SEF) is introduced in this study and denoted by K. It is the ratio of traffic volume in PCU per hour and volume in vehicles per hour. The K factor is related to traffic composition and volume on a road through the regression analysis meth...

Influence of Undesignated Pedestrian Crossings on Midblock Capacity of Urban Roads

Pedestrians crossing an urban road at undesignated places are not uncommon in developing countries such as India, and these people force motor vehicles to provide suitable gaps for their crossing. The present study demonstrates the effect of such crossings on the midblock capacity of an urban arterial road. Data were collected on 12 sections of six-lane urban arterial roads in three populous cities in India. Six sections were selected without any side friction to estimate the base value of capacity. The remaining six sections had pedestrian flow across roads at undesignated crossings. Speed and volume data were collected in the field and were used to estimate the capacity of a section. The base midblock capacity of a six-lane divided urban road was found to vary from 1,500 to 2,100 passenger car units per hour per lane in three cities. This variation was attributed to the different free-flow speeds in these cities. The effect of pedestrian cross flow on the midblock capacity of an urban road was evaluated by comparing the capacity of a section with pedestrian cross flow with that of the base section. Finally, a mathematical relation was developed between pedestrian cross flow and reduction in capacity. The results show practically no influence on capacity when pedestrian cross flow is less than 200 pedestrians per hour. The capacity, however, is reduced by 30% when pedestrian cross flow is increased to 1,360 pedestrians per hour.

Conceptual Approach for Estimating Dynamic Passenger Car Units on Urban Arterial Roads by Using Simultaneous Equations

This study demonstrates that passenger car unit (PCU) values for a vehicle are not static and vary with traffic volume and composition. Data collected at eight urban arterial roads in India were analyzed to explain the dynamic nature of the PCU factor. All vehicles in the traffic stream were divided into five categories, and simultaneous equations were developed to determine the speed of a vehicle type from information on traffic volume and composition. These equations were used to show the variation in PCU values with traffic volume and composition on a road. The change in PCU values was explained on the basis of the relative interaction of vehicle type in the traffic stream at different volume levels. A proposed range of PCU values for big vehicles was from 1.47 to 1.65 for big cars and for heavy vehicles from 5.51 to 6.54, respectively, when their proportions in the mix remained within an observed range in the field. Similarly, a range of PCU values for motorized three-wheelers of 0.99 to 1.01 and a set of PCU values for motorized two-wheelers of 0.20 to 0.23 were obtained. Accuracy of the PCU values estimated through simultaneous equations was checked by comparing the estimated values with those calculated directly from the field data. Statistical testing showed that there was no significant difference between field-estimated and model-predicted PCU values. Further, the speed–volume relationships developed by using two sets of PCU factors yielded the capacity values with a difference of less than 2%; this result indicates the correctness of the methodology in this study.