Analysis of Speed Profiles at An Unsignalised Intersection for Left Turning Vehicles

Document Type : Research Paper


1 Ph.D Candidate, Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran

2 Assistant Professor, Department of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran


Intersections are one of the elements that play an important role in urban networks. Analysis of drivers’ performance at unsignalised intersections is crucial, especially in left-turning movements due to their several inherent conflicts and variety of drivers’ maneuver types which affect traffic safety and capacity at such intersections, so the purpose of this paper is to introduce how the behaviour of drivers will be specified in left-turning at unsignalized intersection. For this study, traffic data were collected using a fixed digital camera. First, the vehicle speed profiles are categorized into descending-ascending slope (type (A)), the smooth descending-ascending slope (type (B)) and ascending slope (type (C)).The effects of the initial speed of left-turning vehicles, the exposure with other vehicles, and the vehicle type (i.e., taxi versus other vehicles) are investigated on the choice of speed profile. A multinomial logit model is utilized to explain how various variables influence the choice of speed profile. The estimated model indicates that the initial speed and the exposures are influential parameters. Also, vehicles with left exposure at intersections increase the drivers’ tendency for selecting type (A) profile while they have low to medium initial speeds when entering the intersections. For the vehicles with high initial speeds, most drivers pass the intersection with type (B) profile. Vehicles with low initial speeds and a low number of exposures increase the probability of selecting type (C) profile. Introduced method can be applied for simulation models at unsignalised intersection to show how drivers will behave in left-turning movements.


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