Abstract
In Hokkaido, as an e fficient improvement that a ffords high-quality service for road users, the intermittent installation of an additional lane to existing two-lane highways (i.e., the creation of 2 +1 lane highways) has been adopted. In this study, the following were targeted as indexes of quality of service for performance evaluation of the road: average traveling speed, follower percent and follower density. Using these indexes, the quality of service achieved by the placement of an additional lane was shown by tra ffic flow simulations and onsite measurements. Two road surface conditions were observed: dry, and compacted snow. Using follower density as an evaluation index, classification of the service level of a two-lane highway in a cold, snowy region was determined. A case study was conducted on the Saraki-Tomanai section of National Highway 40 (between Wakkanai City and Toyotomi Town) in which that section was installed with an additional lane at regular intervals and the following density was measured when the road surface was dry and when it was compacted snow. The measurements demonstrated that the improved road a fforded a service level of A, even when the road surface was compacted snow.
