| The distance between tunnel and service area not only restricts the tunnel and the choiceof service area location directly, but also has an important influence on the traffic safety.Recent years have seen increasing small spacing section between freeway tunnel and servicearea, leading to traffic accidents frequency in this condition, seriously influencing the trafficsafety and the service level of freeway. To improve the security, service level and operationalefficiency of the sections between tunnel export and service area, this paper studies theminimum distance between freeway tunnel and service area.At the first, the distance between freeway tunnel and service area is defined. Throughanalyzing all parts of the minimum spacing, the distance demanding model is established.Considering the influence factors of export to service area distance and the worst drivingpattern, adopting the lane change theory and the secondary reduction theory on decelerationlane, taking to satisfy the demands of vehicle driving on the road as control condition, theminimum spacing in tunnel export to service area calculation model is confirmed andrecommended value of the minimum distance is given.Using traffic operation condition analysis method in "highway capacity manual" of ourcountry, this paper takes density as a major efficiency index to evaluate the quality of theoperation, meeting the target service level as a constraint condition, the maximum servicetraffic volume meeting the target service level as the basic conditions for section microscopicsimulation. The microscopic traffic simulation software VISSIM is used to simulate theoperation condition of the section traffic flow. Based on the selection of evaluation index andthe establishment of evaluation system, the recommended minimum distance between tunnelexport and service area is analyzed to judge whether it meets the target service level, modifythe dissatisfied sections, and further simulate and evaluate the revised results using VISSIM,and then determine a reasonable minimum distance between tunnel export and service area.To those sections with small distance of export to service area which have been built,this paper puts forward corresponding improving measures to improve the road traffic safety.The research in this paper, on existing standard about tunnel export to service area, has acertain practical significance to the technical update of the provisions. |
