Research On Minimum Spacing Between The Mainline Shunt Or Confluence And The Tunnel Or The Main Access

With the improvement of the highway network in our country,in order to meet the requirement of traffic and reconstruction,Highway traffic transportation nodes(such as the mainline shunts and confluences,tunnels,interchanges and service areas,etc)will be more intensive.How to programme all sorts of traffic facilities reasonably and make full use of then becomes the major problem of the construction of the highway traffic facilities.And the spacings between the mainline shunt or confluence and the tunnel or the main access have significant implications on the security of traffic and service level.Therefore,research on minimum spacing between the mainline shunt or confluence and the tunnel or the main access is feasible.The function and form of mainline shunt or confluence were analyzed,and the definition of the spacing between the mainline shunt or confluence and the tunnel or the main access was stated base on them.The influence factors of spacing were analyzed from the aspects of road conditions,traffic flow characteristics,the driver behavior,etc.According to influence factors and the characteristics of the traffic facilities,considering the special case of extreme conditions,analyzing the driving behaviors of large cars and small cars separately,general and extreme minimum spacing calculation models were established under the different combinations and the corresponding recommended values were proposed.Using VISSIM simulation models,adopting evalution system which conflict rate is security evaluation index and fuzzy clustering analysis is evaluation method,verifying the above conclusions,and the logical spacings between the mainline shunt or confluence and the tunnel or the main access were obtained.Through to the features of related traffic facilities and traffic flow characteristics of small spacing section,a series of security measures which give priority to withadvance signs were presented.Research provides the theoretical basis for spacing between the mainline shunt or confluence and the tunnel or the main access to the existing specification and has a certain practical significance.