Construction of Passing-Maneuver Model on Two-Lane Highway with Consideration of Road Surface and Visibility Conditions

Most national highways in rural parts of Hokkaido, Japan, are two-way, two-lane roads. On these highways, passing maneuvers that involve the use of the oncoming lane are frequently observed. Such passing is observed even when road surfaces are covered with compacted snow. To optimize speed and safety, simulated passing maneuvers have been conducted to make use of the oncoming lane of a two-way, two-lane highway. No such traffic simulations, however, have taken into consideration the surface conditions of roads in winter (e.g., snow-covered, icy, with poor visibility caused by snowfall and fog). In this study, a traffic flow simulation to model passing maneuvers that involved the oncoming lane was created through the use of values measured in a passing-maneuver field survey conducted on a two-lane road in summer and winter. The field values for the number of passing maneuvers, traffic volume, and speed distribution were compared with the simulation results. The outcomes confirmed that the difference between them was small. The sensitivity analysis results revealed that the number of passing maneuvers on surfaces covered with compacted snow under conditions of poor visibility did not increase as much as they did on dry surfaces, even when the traffic volume in the original lane was higher. The passing success rate tended to decrease with higher volumes of traffic in the oncoming lane, regardless of surface conditions.