Involvement of vehicle factors in road accidents

Abstract

Road traffic systcm comprises of three components viz. road, vehicle and human. Like roadway fault and human error, defective and road unworthy motor vehicles on road pose a threat to safety of road traffic system. In developing countries. it is likely that vehicle defects are more alien a pronounced factor in accidents as vehicle conditions arc generally much worse. The vehicle Ikct consist usually old reconditioned vehicles or vehicles locally modified with littlc or no consideration at all to passcnger safety. Besides, buses are olien constructed on truck chassis using materials and designs that offer little or no protection to passengers in the event of an accident. Leg room between seats is olien exceptionally poor in order to squeeze the maximum number of seats in the vehicle and the scat frames themselves arc usually formed from angle steel, frequently causing amputation of limbs in an accident. Emergency exits, when provided, arc olien blocked by a row of seats, making their usc dit1icult. Modification of seating arrangement, fixing additional features with the vehicle like strong bumpers. rooliop railing etc arc also pose a great safety hazard. Defective vehicles may emerge as dreadliJl in the realm of ever-increasing road accident menace. The study is carricd out in attempt to identify the most common vehicular defects and their inlluence on road accidents in Bangladesh. In this study accident data collected from the Jamuna Multipurpose Bridge (.1MB) approach roads by the Accident Data Unit (ADU) of JOMAC (the toll collection and bridge maintenance agency) is used. It is found that during the period of 0 1-0 1-99 to 30-04-04, a total of 1013 accidents occurred involving 2155 casualties on about 39 km section of roadway, which includes 14.76 km east approach, 16.54 km west approach roads and 4.8 km long bridge itself. Among these accidents. due to different vehicular faults a total of 1G7 accidents had occurred involving 686 casualties. In terms of the percentage of total accidents the contribution of vehicular defects is calculated IG.G percent and in terms of total casualties caused by the same factor is 3 I .9 percent. The common vehicular faults are identified as tyre bursting, brake failure, axle failure. whecl jam and wheel-off from axle, passenger fall-down Irom rooftop etc. It is found that the most serious vehicular fault is tyre bursting which accounts for 42.5 percent accidents and 83.7 percent casualty of all vehicular defects related accidents, which is followed by passenger fall down from rooftop (7%), brake failure (5.7%), wheel/drum off or jam (2.6%), axle fallen (0.9%) and defcctive light (0.1 'Yo). In terms of the total accidents and casualty the contribution of tyre burst tantamount to about 7.0 percent and 26.6 percent respectively. Due to tyre burst type accidents trucks involved in 59 percent incidcnees and buses involved in 79.8 percent casualties of the total 71 accidents and 574 casualties. It is found that rear tyre burst incidences are higher than front tyre burst incidences, but front tyre burst incidences are more vulnerable than rear tyre burst incidences. Trucks involved in the highest number of rear left tyre burst accidents than buses. Based on the frequency of accidents and field condition survey that the rear-left tyre is found to be the most defective and prone to bursting. Due to break failure type accidents buses involved in more casualties than trucks and light vehicles. Trucks involved in the highest number of casualties due to wheel jam, axle fallen or tie rod broken of 89 percent and 67 percent respectively, lIence, trucks are identified as the most defective and accident-prone vehicle followed by bus and light vehicles respectively. By any comparison these findings are dreadfully higher than those in developed countries. From heavy vehicle's condition survey it is found that front leli tyre and rear left tyre arc more defective than front right tyre and rear right tyre. It is found that spear tyre, brake system, wheel, wiper, exit door and sitting arrangement modification of vehicles are found poor or absent in 32 percent, 18 percent, 43 percent, 50 percent, 64 percent, and 75 percent of vehicles. It is also found that 46 percent vehicles have no fitness certificate, 88 percent buses have railing on rooftop and 75 percent buses engine cover have modif1ed for passenger seat, Questionnaire survey as well as vehicle condition survey reveled that the rampant use of rubber lining tyre, unrestricted import of lower quality tyre, inadequate and insufficient fitness checking arrangement, lack of vehicle fitness checking in the field, poor vehicle maintenance practice, modification of vehicle specification, improper way of vehicle overloading, general tendency of delerring the replacement of defective parts by vehicle owners etc. arc identified as the mitior underlying causes of vehicular defect related problems.