| Hokkaido of Japan is a cold、 snowy island、 where winter、 a season when snowfall is recorded、 lasts for approximately five months from November to March. Therefore、 road surfaces are usually dry but frequently covered with compacted snow. A measure to improve existing two-lane highways to “2+1 lane” highwaysby installing an auxiliary lane has been introduced to offer a better quality of service to road users. A sensitivity analysis was undertaken using a traffic flow micro-simulation program “SIM-R” to evaluate the effectiveness of “2+1 lane highway” sections、 which were built by adding an auxiliary lane to rural two-lane highways、 in a cold、 snowy region. The road surface conditions analyzed were dry and covered with compacted snow. The hourly traffic volumes were changed from 100 to 1、000 vehicles/hour. As evaluation indicators、 the average travel speed、 the percentage of following vehicles and the density of following vehicles were used. As results、 they were found that the average travel speed decreased、 the follower percentage increased、 and the follower density increased、 according to increasing the hourly traffic volumes. Moreover the road performance decreased on the compacted-snow-covered road compared with the dry road. It was also found that the installation of an auxiliary lane at certain intervals improved the level of service for two-lane highways both on the dry road and the compacted-snow-covered road. |
