Study On The Length Of Speed-change Lanes Of Interchanges In Mountain Cities

Due to the limited construction space and flexible road layout,mountainous cities are characterized by the prevalence of small-scale interchanges,two adjacent interchanges or ramp entrances are too close,and the roads have many steep slopes,resulting in different vehicle traffic characteristics on mountainous city roads.The speedchange lane is an important point of intersection of the speed change and lane change of the interchange.Because its complex structure,large changes in driving speed,and the concentration of interlacing and changing lanes,the speed-change lane is not only a common point of urban road traffic congestion,but also the "bottleneck" of the entire intercommunication capacity and accident-prone areas.Therefore,in order to make the length of the interchange speed-change lane in mountain cities play a safe,efficient,and comfortable traffic service function,this article is based on the vehicle traffic characteristics of the area affected by the division and confluence of mountain cities,and studies the acceleration and deceleration lane lengths of the interchange in mountain cities,and the slope of the speed change lane.research.Starting from the analysis of influencing factors in the design of the length of the speed-change lanes,based on the statistical results of the traffic characteristics survey data,the traffic characteristics of the vehicle traffic in the sub-and merge-influenced areas of mountain cities are analyzed.Small passenger cars and buses are the main research objects,based on the theory of vehicle insertion gaps and the front of the vehicle.Timedistance distribution theory,establishes a model for calculating the length of accelerating lanes in mountainous cities that meet the service level of the main line for the purpose of accelerating,waiting for insertable gaps and safely merge into the main line;taking small passenger cars as the main research object,based on the theory of secondary vehicle deceleration,Considering the most unfavorable situation of vehicle deceleration and diversion,a calculation model of deceleration lane length in mountain cities is established in which diversion vehicles transfer lanes on the deceleration lane and decelerate and divert.Based on field survey data and relevant domestic and foreign regulations,the values of the key parameters in the calculation model are given,and the recommended values for the acceleration and deceleration lane lengths of interchanges in mountainous cities in my country are derived.At the same time,the problems existing in the slope correction of the length of the existing speed-change lane were analyzed.Based on the vehicle dynamics principle,the calculation formula of the average ramp acceleration and deceleration speed was calculated.According to the calculation model of the length of the speed-change lane of the mountainous city interchange,the slope correction model of the length of the acceleration and deceleration lane was established.Combined with the interchange of mountain cities,the key parameter values of deceleration lane length and the recommended length values,the recommended slope correction values of the length of uphill acceleration lane,downhill acceleration lane,uphill deceleration lane and downhill deceleration lane under different slopes were deduced.The research of this paper starts from the actual traffic characteristics of the speedchange lanes of the mountain city interchange,and studies the acceleration lane length,deceleration lane length and slope correction of the mountain city interchange.This has important guiding significance and practical value for the road planning and construction of mountain cities.