Adoption of Mixed Logit Models and Observational Before-After Studies to Assess the In-Service Safety Performance of Signalized Intersections and Roundabouts in the Emirate of Abu Dhabi

Intersection-related crashes have accounted for one-third of all road-related deaths in Abu Dhabi City. Several research studies conducted in North America and Europe have consistently shown that converting signalized intersections into roundabouts leads to safety benefits, especially in terms of reducing the number of severe injuries. These studies have led North American and European transportation agencies to convert hundreds of signalized intersections into roundabouts over the last few decades. Meanwhile, the Emirate of Abu Dhabi, the largest emirate in the United Arab Emirates (UAE), has replaced many of its long-standing roundabouts with signalized intersections despite the fact that no UAE-based scientific study comparing the safety performance of these two intersection types can be found in the literature. Hence, the objectives of this paper are to:

Identify crash, road, traffic, intersection, vehicle, and injured-person-related characteristics that significantly contribute to more severe intersection-related injuries;

Assess the in-service safety performance of signalized intersections and roundabouts based on crash- severity modeling procedures; and

Conduct before-after studies using crash and traffic volume data pertaining to intersections which were converted from signalized intersections into roundabouts in order to assess the impact of this conversion on crash frequency and severity.

It is anticipated that the findings from this research will benefit the UAE significantly as it will provide road designers and decision-makers with much needed scientific guidance on whether converting existing roundabouts into signalized intersections improves public safety. This is relevant from a safety standpoint not only because preliminary analyses have found that intersection crashes are disproportionally represented in Abu Dhabi's fatal road crash statistics, but also because Abu Dhabi may continue to convert its long-standing roundabouts into signalized intersections over time.

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