Benefit Evaluation And Design Elements Of Auxiliary Lane On Two-lane Highway

Given the universal usage of the two-lane highways and the lane number restriction, each lane can provide the passing of only one direction and the lane for oncoming traffic have to be used when faster drivers get around slower vehicles.When encroaching into the lane for oncoming traffic, series of operations have to be made with the errors of safety judgment and the road environment perception, which makes overtaking a behavior of relatively high risks and failure rates. The accidents caused by collisions with oncoming vehicles are heavier than other types of accidents, which forms a threat to people’s life and property. So it is a key issue to induce the number of accidents and increase the safety performance on two-lane highways in this article. The auxiliary lanes, which are built somewhere in the same direction for the slower vehicles, make the overtaking of faster drivers a safer behavior without the usage of oncoming lane.The calculation model of safety benefits on auxiliary lane is established by the theory analysis on the number of overtaking accidents and corresponding losses. By analyzing the traffic operation on two-lane highways and application of transportation economics, a computation model of operation efficiency improvement is also built. Furtherly, based on the two models above and having taken the construction and maintenance costs into consideration, the calculation method for net benefits of auxiliary lanes has been proposed.Based on the calculation method for net benefits above, a target function with positive net benefit value has been determined by means of theoretical analysis and questionnaire survey. By proceeding the data collected, constraint conditions of traffic volume and construction costs in the target function has been given. Based on the target function and the constraints above, the calculation model for the spacing distance has been determined and the suggested distances of various design speeds have been given.From the perspective of traffic delay and driving safety, the length, width and critical positive slope values of auxiliary lane have been given with various design speeds, during which both theoretical analysis and traffic numerical simulation have been applied.