Effect of non-motorized transport on the performance of road traffic in metropolitan Dhaka

Abstract

Road based transport in metropolitan Dhaka consists of an integration of motorized transports, non-motorized transports (NMfs) and walking. Besides motorized transports there are about 400000 rickshaws, 10000 rickshaw vans,. 3000 pushcarts, and over 40000 bicycles in nonmotorized transport group (DITS, 1993). According to DITS (1993) NMfs account for 56.7 percent of daily vehicle kilometers of travel in metropolitan Dhaka. Present scenario of transport modes and travel pattems clearly reveal that road transport in metropolitan Dhaka is predominated by NMfs. But in the past, these modes of transport were given very little consideration in transport planning as well as in the selection of management schemes to alleviate traffic problems (viz. traffic congestion, delay, accident, emission etc.). This study is an attempt to investigate the effect of NMfs on road traffic performance (i.e. mobility, speed and safety), which would provide useful information towards solving existing traffic problems in the metropolis. Traffic volume and speed studies were performed at selected road links in order to determine the volume and composition of traffic as well as their speeds. Mobility in terms of personsl hr were determined in the selected road sections using the volume, composition and average occupancy data of each vehicle category. Mean speeds of different types of vehicles as well as of the Link traffic were also calculated from speed distributions of the vehicles at the selected sites. Analysis of fOJlrlane divided major roads showed an average mobility of about 15000 personslhr without NMfs in the link traffic and about 9000 personslhr with 45 percent NMfs in the links. Speed analysis showed an average speed of 21 mph without NMfs and 16 mph with 45 percent NMfs in the traffic of the links. Moreover, an attempt was made to develop mathematical relationships for both mobility and speed in terms of the composition of traffic and road geometry. Formation of models on the basis of multiple linear regression technique and related statistical analysis were performed using a standard statistical computer package SPSS release 6.0. The model, with mobility as the dependent variable, shows that mobility of a road section decreases with the increase of NMf s in the link traffic. Another model, with mean speed as the dependent variable, indicates that speed decreases with an increase of NMfs in the link traffic and increases with an increase in the effective road width. Accident data for different thana zones in metropolitan Dhaka were also collected from available documents to examine the role ofNMfs in road safety. Modal share of total accidents (fatality, injury and property damage) showed that NMfs share of accidents is lower (rickshaw 12 %, other NMfs 2 %) than the share of motorized modes (truck 18%, mini-bus 17%, autorickshaw 11%, car 11% etc.). However, when only fatalities are considered, the share of NMTs, especially rickshaws, become much higher (26%) than that associated with motorized transports (bus 14%, tempo 14%, motorcycle II %, truck 9%, autoricksaw 9% etc.). Furthermore, accident. data in those selected links where volume and speed studies were performed, were identified to develop mathematical relationship. The model, which has been formed with the number of accidents in one year as the dependent variable, indicates that accidents increase as the speed ratio of motorized and non-motorized transports increases and that accident decrease with an increase in effective road width.