The population in the urban area has continuously increased with the economic growth in the country, and also the travel demand by automobiles has rapidly increased with the spread of the boundary and the increase of the population in the urban area since 1980’s. Accordingly, the increase of the travel demand is in a situation causing the transportation problems, such as traffic congestion, traffic accident, and air pollution by automobiles, which was thought to be one of the severe problems out of the urban problems. Out of these transportation problems, traffic congestion occurring on the roadway is primarily the phenomenon occurring when the travel demand exceeds the roadway capacity, or the roadway capacity decreases below the travel demand. This causes the social loss of cost as a factor of the representative external diseconomy by the travel activity, except the difference in the level of congestion depending on the travel space and time period.
One of the solutions for relieving traffic congestion is continuously to build the new roadway facilities or expand the existing roadway facilities for increasing the roadway capacity which could handle the increasing travel demand, but the limits are somewhat faced with in handling the travel demand only by the supply of the physical transportation facilities, because building the new roadway facilities or expanding the existing ones needs the huge invested funds. So the transportation demand management(TDM) program has began to gain power for controlling the travel demand as a proposal to relieve traffic congestion in a city or a specified area of the city since the late 1980’s.
As one of the TDM programs, the congestion toll(CT) pricing program is not a program to easily get the agreement from the roadway users because it has a weakness to economically restrict the mobility of the roadway users. However, it is required to differently impose the congestion tolls on the roadway users by the congestion level of the roadway, because the CT pricing program is the alternative program which can get out of the external problem of transportation like an environmental problem and regulate the travel demand by the space and time for using the roadway efficiently.
Thus, on the premise of the introduction of the electronic toll collection system(ETCS) which is one of the intelligent transportation systems(ITS) the purpose in this study is to analyze the traffic characteristics and interrelationship between the traffic characteristics collected on the mainline sections of the inbound and outbound directions of the urban freeway under the study, derive the CT computational function with the speed elasticity and the traffic flow models before predicting and evaluating the congestion toll, and finally suggest the optimal CT predictive and evaluative model by comparing the congestion tolls predicted and evaluated.
From the analyses of the CT predictive and evaluative model, the congestion level was shown to be considerably different according to the spatial scope and the traffic flow models in the inbound and outbound directions. Also, the variable CT pricing program proved to be more efficient than the uniform CT pricing program by showing that the congestion toll was predicted to be low when speed was high, and predicted to be high when speed was low. Additionally, the congestion toll was shown to be extremely high when traffic flow arrived at the maximum flow condition, which was not a realistic congestion toll by imposing a high burden of cost on the roadway users. However, it showed that the total social cost was decreased by the increased cost of each trip even though the low congestion toll was imposed at the maximum flow condition (i.e., the oversaturated flow condition). So it was judged that the congestion toll must be priced depending on the speed intervals considering that the classified congestion tolls were not higher than the unclassified ones in order to minimize the repelling of the roadway users.