Research on the evaluation of traffic condition using mobile phones

Road traffic jam is a major source of inefficiency and wasted fuel. Measuring and localizing the congestion is an important step towards reducing the time people spend stuck in traffic. With the rapid development of phones, smart phones can provide location estimates with GPS sensor. Using position samples from drivers' phones to monitor traffic delays opens up the possibility of road condition estimation. This paper describes a road state evaluation system using the GPS data obtained from mobile phones. First is to evaluate the link average speed of a single vehicle, piecewise cubic Hermite interpolation method is employed to improve the accuracy of evaluation. Concerning that the speed of the same type vehicle is relatively stable, next is to obtain this parameter using the method of weighting. Last, use the average speed of different types of vehicles and ratio of those types as the inputs, and the link average speed as the output to construct the RBF (Radical Basis Function) neutral network. With the network, we can get the link average velocity, and according to the statistical analysis we know the number of the vehicle in the period of time, so the traffic flow is easy to calculate. We present experimental results from 24 different link groups of bus GPS data, the analysis result proves that the piecewise cubic Hermite interpolation method has a better performance and less error than traditional linear interpolation method. We show that after training the RBF network with large volumes of data obtained from VISSIM, the proposed evaluation method has a good performance.