Traffic flow on urban road links is usually interrupted by different factors within the road environment. These factors are referred herein as sidefriction factors. These 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 traveled way. Four typesof such factors were studied on arterial roads in Dar-es-salaam, Tanzaniaand their impact on the free-flow speed of vehicles was measured. These included pedestrians walking along road shoulders, bicycles riding in the traveled way, non-motorized vehicles driving in the traveled way, and vehicles pulling up on shoulders or entering the traveled way from the same. Data were collected on four lane-two way and two lane-two way roads by application of video methods, and the analysis was based on statistical methods, chiefly regression analysis. The results showed significant impact on free-flow speed for both road types, such that each friction factor depictedsome impact of some magnitude in terms of speed reduction. Recommendations were made based on these results that they can be useful for attaining appropriate urban traffic management schemes.
Abstract