Research On The Travel Time Reliability Impacted By Network Performance Degradation

With the development of social and economics, the requirements on travel time and reliability is higher. However, natural and human factors increased uncertainty of roads supply, seriously affecting people's efficiency of production. It's more and more important to study variation of travel time reliability.Obtaining degradation factors by Fault Tree Analysis, then study mechanisms from supply and demand aspects. According to above, we make degradation parameters as a function of road quality, traffic management, weather conditions, natural disasters and human factors.Road capacity can be expressed as the product of degradation parameters and design capacity, then relationship of travel time and parameters can be obtained. With the approximation function of normal distribution, the relationship between travel time reliability and degradation parameters can be reached. First derivative is the marginal benefit of travel time budget, and the conclusion is: risk performance travelers'marginal benefit accelerated with increase of budget travel time, and conservatives'growth slowed down, the optimum is where the expectations and budget travel time are equal, Which is vertified by simulation case.Based on the conclusions, the marginal benefit curve can be reached, and the minimum acceptable marginal benefit curve is available for different situation. The intersection of above two curves is the traveler's best budget travel time, which is maximum efficiency point.The conclusion can guide the people's travel to optimization, also offer reference for traffic manager and planner.