Driving Behavior Test on Roundabout with Road Surface Changes

To ensure safe driving, it is very important for drivers to appropriately perceive road alignment, pavement markings, various road accessories and road surface conditions. However, road surface conditions change with the weather, and in cold, snowy regions can vary widely from dry to wet to compacted snow during the winter months. Compacted-snow-covered roads pose a range of problems, including preventing drivers from seeing pavement markings and making roads slippery. As the northern part of Japan is characterized by the harsh weather conditions commonly seen in cold, snowy regions, there is increasing interest in the evaluation of drivability and safety for modern roundabouts in various weather and road surface environments. The authors installed a small single-lane roundabout for experimental purposes on the Tomakomai Test Track in Hokkaido, Japan, in autumn 2009 and winter 2010 to enable related driving tests. A total of 16 subjects participated in these tests and drove test vehicles, some of which were equipped with a driving-behavior monitoring system. The road conditions tested were those with dry and compacted-snow-covered surfaces. After a period of driving involving the roundabout, the drivers were asked to answer a questionnaire indicating subjective assessment of drivability and safety. The results showed that the speeds of vehicles approaching the roundabout when the road was covered in compacted snow were lower than when dry, thereby demonstrating a greater speed reduction effect. Subjective assessment suggested that drivability and safety in compacted-snow-covered road conditions were much lower than those in dry road conditions.