title: Risk appraisal of passing zones on two-lane rural highways and policy applications.
abstract: Passing on two-lane rural highways is associated with risks of head-on collision resulting from unsafe completion of passing maneuvers in the opposite traffic lane. In this paper, we explore the use of time-to-collision (TTC) as a surrogate safety measure of the risk associated with passing maneuvers. Logistic regression models to predict the probability to end the passing maneuver with TTC less than 2 or 3s-threshold were developed with the time-gap from initiation of the maneuver to arrival of the opposite vehicle (effective accepted gap), and the passing duration as explanatory variables. The data used for model estimation was collected using stationary tripod-mounted camcorders at 19 passing zones in Uganda. Results showed that passing maneuvers completed with TTC less than 3s are unsafe and often involved sudden speed reduction, flashing headlights, and lateral shift to shoulders. Model sensitivity analysis was conducted for observed passing durations involving passenger cars or short trucks (2-3 axles), and long trucks (4-7 axles) as the passed vehicles for 3s TTC-threshold. Three risk levels were proposed based on the probability to complete passing maneuvers with TTC less than 3s for a range of opposite direction traffic volumes. Applications of the results for safety improvements of two-lane rural highways are also discussed.
authors.affiliation: Department of Civil and Environmental Engineering, School of Engineering, Makerere University, Technology Road, P.O. Box 7062, Kampala, Uganda. Electronic address: gmwesige@cedat.mak.ac.ug.
authors.forename: Godfrey
authors.initials: G
authors.lastname: Mwesige
authors.affiliation: Department of Transport & Planning, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628 CN Delft, Netherlands. Electronic address: H.Farah@tudelft.nl.
authors.forename: Haneen
authors.initials: H
authors.lastname: Farah
authors.affiliation: Department of Transport Science, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Teknikringen 72, 1tr, 100 44 Stockholm, Sweden; Northeastern University, Boston, MA 02115, United States. Electronic address: hnk@kth.se.
authors.forename: Haris N
authors.initials: HN
authors.lastname: Koutsopoulos
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D001334:Automobile Driving; D006801:Humans; D016015:Logistic Models; D008962:Models, Theoretical; D018986:Motor Vehicles; D057766:Policy; D011336:Probability; D012044:Regression Analysis; D012424:Rural Population; D012449:Safety; D014454:Uganda
keywords: Accepted gap; Passing duration; Passing zones; Risk; Time-to-collision; Two-lane highways