Minor-Street Vehicle Dilemma While Maneuvering at Unsignalized Intersections

The drivers on a minor approach at an unsignalized intersection intending to maneuver are usually at risk because of the difficulty in judging if available gaps are safe or not. Any misjudgment may result in collision with major-stream vehicles. Drivers are clear about rejecting small gaps and accepting large gaps, but experience dilemmas for a range of gaps. This paper is an attempt to study the dilemmas of minor-road vehicles intending to cross the major road. It has been reported in past studies that drivers in India are more aggressive and often accept very small gaps, creating dangerous situations. The authors analyzed variations in spatial gap-acceptance behavior by different drivers and arrived at dilemma-zone boundaries. Field data were collected at four uncontrolled intersections with posted speeds of $40\mathrm{km}/\mathrm{h}$ (medium-speed intersection) and $60\mathrm{km}/\mathrm{h}$ (high-speed intersection). Drivers’ behavior intending to cross a major street is modeled as a binary decision (accept or reject a gap). The distribution of the dilemma zones was analyzed for different speeds and categories of conflicting vehicles and times of day (i.e., day versus night). Speed, vehicle type, and time of day had a statistically significant effect on both the length and the location of the dilemma zone. Dilemma zones can be further used to develop driver assistance systems to improve driver safety by assisting them in making the right decision in critical situations at uncontrolled intersections. Although the study intersections are in India, where road traffic, like that of other developing countries, is characterized by aggressive drivers, the concept and methodology are useful in developed countries, too.