The standard methods of calculating intersection capacity develop general values for saturation flow rates for left-turn lanes at signalised intersections. The Highway Capacity Manual (HCM 1985) adjusts the dual left-turn volume by a factor of 0.92. Various articles indicated results that differ from the HCM method, particularly in the distribution of vehicles in the dual left-turn lanes. This paper studies the saturation headways in the inside and outside dual left-turn lanes, distribution in lanes and effects of striping and geometry. A total of 2735 data points was collected and subjected to statistical analyses. The results show a statistically significant difference in the saturation headways in the saturation headways of the inside and outside left-turn lanes at 95 per cent confidence level. Generally, the left-turn lane use is 46 per cent for the inside lane and 54 per cent for the outside lane excluding special cases of geometry and striping. These results are in close agreement with Transportation Research Record 212. (A)
Samenvatting