Truck Use of Newly-Installed Roundabouts on the Kumasi-Ejisu Section of the Accra-Kumasi-Gonokrom Road (Route N6)
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Date
2008
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Abstract
Truck use of four newly-installed roundabouts on a rehabilitated section of Route N6 in Ghana was investigated. The study was motivated by public opposition to the roundabouts as a result of the occurrence of a number of accidents, particularly truck accidents, shortly after the rehabilitated section had been opened to traffic. The study involved observation of truck driver manoeuvres at the roundabouts, interview on truck driver knowledge of use of the device, and review of the accident records for as well as the as-built drawings of the roundabouts. Of a total of 16 accidents that have occurred to date since the installation, seven (46.7%) involved trucks with all the truck accidents taking place only at a particular roundabout (the University Police Station Roundabout). Of the seven truck accidents, five involved vehicle rollover (overturning). A comparison of the accident records at the intersections before and after conversion to roundabouts did not point to deterioration in safety following conversion except for the intersection at the University Police Station where the reverse was the case. Of 240 truck drivers interviewed who use the route, none knew the essence of the truck apron forming part of the roundabouts as they all considered tracking the apron a traffic offence and as many as 185 (77.1%) said they never use the apron. This perception was well corroborated by the results of the truck manoeuvre study at one of the roundabouts in which 150 (80.2%) of the 187 trucks captured on video manoeuvred the roundabouts in such a way as to avoid tracking the apron. All the drivers interviewed admitted that avoiding the truck apron made manoeuvring the roundabouts very difficult as it required extra caution especially when their vehicles carried load because of the possibility of load shifting. No significant differences existed between the roundabouts in terms of geometric details except that the topography at the location of the roundabout with the highest accident record was relatively steeper than that at the other roundabout locations. It is believed that the high incidence of truck overturning accidents at the University Police Station Roundabout could be attributed to a combination of a possible vehicle imbalance caused by load shifting as the truck drivers manoeuvred to avoid tracking the truck apron and the unfavorable gradient at that roundabout. The installation of the roundabouts should have been preceded by elaborate driver education on how to use the device.
Description
A Thesis Submitted to the Department of Civil Engineering, Kwame Nkrumah University of Science and Technology in Partial Fulfilment of the Requirement for the Award of the Degree of Master of Science.