Fuzzy logic methodology to evaluate the service level of freeways basic segments

Based on fuzzy logic, a methodology is developed to evaluate the level of service of the basic segments of freeways. For this purpose, the four most important parameters known as the "characteristic parameters for evaluating the freeway service level" are being used. In this study, according to the approaches given in Highway Capacity Manual (HCM), as well information obtained by some highway transportation experts, some primary values of the parameters based on the corresponding membership functions are chosen. The methodology developed herein can be used as a basic approach in order to evaluate the service level of freeways. As a numerical study, three freeways are chosen. In order to show the effect of some important parameters such as speed, density, and so on, on the service level of freeways, parametric studies are carried out. It is found that the freeway service level significantly depends on the density of the traffic.