Study Of Driver Decision-making Assistance Based On The Safety Distance In Car-car Communication

The survey indicates that most malignant accidents are rear-ending collisions. Especially in the condition of lack of sight distance and road adhesion coefficient reduced, rear-end chain accident happen easily. The accident not only caused heavy casualties but also brought huge economic losses and caused traffic jams. Residents'travel will be affected by the accident. Nowadays the development of computer technology, communication technology and intelligent transportation technologies provide technical support and theoretical guarantee for car-car communication technology. This idea has become a hot research in providing security information for drivers. And the security alarm made in terms of safety distance between vehicles.The safety distance model in this paper is based on the thought of car-car communication. And it analyze the single lane fleet vehicle which is under car-following status (the car-following status is that the headway is less than 6s). Firstly, the reference car is considered to be the one with minimum speed in the fleet, then divide the fleet into two sub-fleet by this dividing points, and dived the frontal fleet with the same method. Each fleet consist the minimum speed car, the adjacent minimum speed car and other cars. Analyze the safe distance and provide decision information for cars in different locations.For the smallest speed vehicle in the sub-fleet, their speeds are less than the speed of the vehicle in front. The distance between two vehicles is gradually widening. So this safety distance can not be considered and regard as the distance is the distance which after two vehicle braking stop should be maintained. The drivers should pay attention to raising the speed and its recommendations speed is the speed of the adjacent front vehicle. For the vehicle which close to the minimum speed vehicle, the vehicle in front of it may have four kinds of motion states: stationary, slow movement, uniform motion and accelerated motion. Stationary means the speed is zero. The first two states are amalgamated into single one. And the distance calculated in this state is consided the absolutely safety distance between vehicles. When vehicle accelerate driving, the distance between vehicles will gradually increase and the vehicle is in a safe state. The distance calculated in uniform motion state is consided the relatively safety distance between vehicles. Similarly, the safety distance model between the rest of vehicles established in terms of the smallest speed in the fleet. Because the speed of vehicles behind will not greater than the smallest speed in long time. So the calculated distance is that the safety distance should be maintained when two vehicles slow down to this speed. The recommendations speed is the minimum speed in the fleet.The safety distance model is established based on the car-car communication and the braking process of vehicle. The acceleration of vehicle varies with braking force, so the security model is established on the basis of actual measured acceleration. Calculating the safety distance of three-vehicle model in the three states above and analyzing the traditional safety distance model prove that this model can prevent vehicle rear-end accidents well, and can raise the road utilization rate to some extent. The feasibility of the method is verified through the decision-making simulation, and the rear-end chain accidents can be prevented effectively.