The Research On The Vairable Speed Lane Setitng Up At Tunnel Portal Under Special Conditions

The express-way has developed rapidly in recent years in China, which has playeda huge role in national economic development. As the national central and easternregions more perfect of the express-way network, express-way’s constructionconcentration with height has also been transferred to western regions where theeconomic development is relatively backward. And western region especially insouthwest of China, topography conditions of mountains and rivers had a greatinfluence on express-way construction. Expressway interchange is the multi-layerspatial structure that connected to the two express-ways or highway with other of levelroad. Interchange is an important part of expressway.Small clear distance between tunnel portal and express-way interchange situation isoften encountered in Mountainous area. In order to ensure traffic safety, road designerusually take a mutation or change interchange form set the location of the methods toimprove the distance between tunnel portal and interchange. These solutions in theimplementation process, restricted by terrain conditions, will produce larger quantity orincrease construction difficulty of the project implementation, investment costs andenvironmental benefits are adversely affected.Tunnel is given in this paper to broaden a variable speed lane, vehicles that put offthe freeway mainline will change lanes to variable speed lane, then gone to thedeceleration lane of interchange that connected the tunnel portal. This paper throughanalysis the driver’s driving behavior and driving environment inside the tunnel,proposed tunnel set method and position of traffic signs; Vehicle lane-changing modelcalculation and analysis are used to determine the tunnel to the variable speed lanelength; And through comparison with other interchange scheme finds out theengineering applicability. This paper proposed design theory and method of broaden avariable speed lane for highway designer reference, under the condition of smallspacing between tunnel portal and interchange.