Speed-change Lane Length Value Research Based On The Cost-benefit Analysis

Speed-change lane as an important part of the interchange, contenting acceleration and deceleration lanes, its main role is to provide an entrance and exit for the inlet and outlet vehicles of the main line, and to provide a acceleration and deceleration process for the vehicles achieving the main line or the ramp line phase adaptive speed. Because in this interval period vehicles have to complete lane transformation and speed change, speed-change lane is often the frequent accident occurring section of the interchange. Reasonable length selection of speed-change lane has a particularly important sense on both saving construction cost and reducing the number of traffic accidents.The study concludes that the longer speed-change lane can effectively reduce the number of traffic accidents, on the other hand, it will no doubt increase the construction cost of speed-change lane, so how to comprehensive consideration of the traffic safety and construction cost, putting forward reasonable length selection standards of speed-change lane are an issue that is worth studying.This paper first introduced the length determination methods and technical standards of the speed-change lane of the interchange, and analyzed with the length design standards of the speed-change lane of our country interchanges, and then introduced the method of determining the length of acceleration lane based on the probability and statistics model, but the present research on the speed-change length both at home and abroad, is based on the design speed. This paper conferring the research of the scholars both at home and abroad, introduce the cost-benefit analysis theory into the research of determining the length of the speed-change lane, build the cost model, the accident model, the loss model, transform the construction cost and accident loss into present value and then compare them. Finally puts forward the best reasonable length range of speed-change lane when the benefit-cost ratio corresponding reaching the maximum value, it can save construction cost to the greatest extent, and can bring the most social economic benefit by reducing the number of traffic accidents.