Study On Lane Changing Safety Spacing Model Of The Basic Freeway Section

With the development of freeway in our nation, the loss of people property and lives caused by traffic accidents becomes more and more large. As an important part of freeway, the safety level of the basic freeway section is of great significance on vehicle operation. One of the riskiest maneuvers that a driver has to perform in a conventional highway system is to perform a lane changing maneuver. For collision free vehicle following, the spacing should be large enough in order to guarantee no collisions during all possible vehicle maneuvers.Owing to the complexity of lane changing and the restriction of traffic safety management on vehicles, there is not any modeling method successfully applied on vehicle development and traffic accident avoidance as yet.Based on the domestic and foreign lane changing model, the minimum safety model is built on theory, and the following research work has been done combined with lane changing running characteristic.Firstly, it analyzes the kinematics of the vehicles involved in a lane changing maneuver, and studies the conditions under which lane changing crashes can be avoided. That is, given a particular lane change scenario, to calculate the minimum longitudinal spacing which the vehicles involved should initially have so that no collision, of any type, takes place during the maneuver.Secondly, it calculates special cases of lane changing scenarios in the study. For the cases where the merging vehicle moves with either constant longitudinal velocity or acceleration, it explicitly calculates the MSSs and shows that the regions in the initial longitudinal spacing/relative longitudinal velocity plane can be divided into safe and unsafe regions; Once the vehicles start the lane changing maneuver within the safe regions then collision-free maneuver is guaranteed.Then, it assumed in the simulations that all vehicles, involved in the lane changing maneuver, were initially at steady state, i.e. their velocities were constant prior to the maneuver. Except for the merging vehicle, all vehicles keep their steady state velocity during the merging maneuver. Three different longitudinal acceleration scenarios-constant longitudinal velocity, switching longitudinal acceleration, and modified switching longitudinal acceleration-were applied to the merging vehicle in order to determine the safe and unsafe region as well as the MSS between the merging vehicle and its surrounding vehicles. It observed that the switching scenario and the modified switching scenario expanded the safe region for lane changing. Furthermore, by considering the longitudinal adjustment acceleration for the merging vehicle, the possibility of moving from the unsafe region into the safe region was studied.Lastly, using driving simulator to simulate the road test, it memorizes the vehicle running parameter in real time. Compared the simulation results with the academic values, it proves the validity of the MSSs.These results will mainly apply guidance to lane changing, and provide warnings. It's of great importance for engineering practice.