EFFECT OF SIDE FRICTION ON CAPACITY OF URBAN ROADS

Abstract

Side friction factors are defined as all those actions related to the activities taking place by the sides of the road and sometimes within the road, which interfere with the traffic flow on the travelled way. They include but not limited to pedestrians, bicycles, non-motorised vehicles, parked and stopping vehicles. These factors are normally very frequent in densely populated areas in developing countries, while they are random and sparse in developed countries making it of less interest for research and consequently there is comparatively little literature about them. The objective of this thesis is to analyze the effect of these factors on capacity of urban roads. The present study is mainly focused on individual effect of the friction factors like presence of a bus stop, on-street parking and pedestrians crossing the road on capacity of urban roads. Data on three sections of 6- lane divided road and two sections of 4-lane divided road were collected in New Delhi and Jaipur with no side friction. These are taken as the base sections. Three basic parameters of traffic speed, volume and density are used for estimation of traffic carrying capacity of a road. For determination of speed-volume relationship in heterogeneous traffic condition, the volume calculated by total vehicles recorded for each counting period were converted into equivalent number of PCUs. Mean stream speed or weighted space mean speed is calculated and used in the present study. The present study demonstrates that mix traffic stream can be converted in to an homogeneous equivalent of passenger cars by multiplying the total traffic volume (in veh/hr) by a stream equivalency factor (K). It will avoid the problem of estimation of PCU values for individual vehicle categories in the traffic stream. The stream equivalency factor (K) will depend on traffic composition and a regression equation is developed in this study to estimate K-value on urban roads. The capacity of 4-lane and 6-lane divided urban arterial roads in present study is estimated at 2050 pcu per hour per lane for no side friction condition. The effect of bus stop on the traffic stream is to reduce its speed and capacity of the section. A bus stop located on curb lane reduced the capacity by 12 and 15 percent respectively. The effect of on-street parking on the traffic stream is also to reduce capacity. On-street parking reduced the capacity by 38% which is quite substantial. At one location (section VIII) where vehicles were in continuous slow motion and there was no halt for a longer duration, the capacity was reduced by 6 percent only. The pedestrians crossing a road will interact with vehicular traffic and thus reduce the capacity of the road. Reduction in capacity will however, depend on pedestrian cross-flow. Capacity reduced to almost half (49% reduction at section XII) when pedestrian cross-flow was 1360 peds/hr and reduction was only 15% for a pedestrian cross-flow of 508 ped/hr. Keywords: side friction factors, capacity, urban roads. iv