PURPOSES : This study is to analyze the reduction effect on road pavement damage from the installation of weigh-in-motion systems used for overloaded vehicle enforcement, from the perspective of traffic assignment. METHODS : Fixed-demand multi-class traffic assignment was conducted by VISUM, a macroscopic traffic simulation software. We considered three vehicle classes and calculated the traffic load for each road link using the ESAL(Equivalent Single Wheel Load) factor, as proposed by ASHTTO(American Association of State Highway and Transportation Officials). We set up scenarios with weigh-in-motion installations in certain sections and observed how the traffic load changed before and after the installation of weigh-in-motion for each scenario. RESULTS : Three main trends were observed. Firstly, at points where weigh-in-motion systems were installed, traffic load significantly decreased even with the influx of cars and trucks following the restriction of overloaded trucks, highlighting the significant influence of overweight vehicles on the traffic load. Secondly, even when overweight vehicles detoured, there was no significant change in the overall network's traffic load. Lastly, the detour of overweight vehicles led to an increase in the total driving distance and time for all vehicles. CONCLUSIONS : Installing weigh-in-motion systems in sections with a lower structure number, which indicates thinner road pavement, can prevent damage in those specific areas without affecting the entire road network.

PURPOSES : This study aims to develop an algorithm to solve the user equilibrium traffic assignment problem using soft link capacity constraints. This model is used to relax the hard capacity constraints model. METHODS : In the traffic assignment model that imposes the hard capacity constraints, the well-known solution algorithms used are the augmented Lagrange multiplier method and the inner penalty function method. The major drawback of using the hard-capacity constraint model is the feasible solution issue. If the capacities in the network are not sufficient to absorb the flow from the diverged flows through the hard capacity constraints, it might result in no solution; whereas, using a soft capacity constraint model guarantees a feasible solution because the soft capacity constraint model uses the penalization of constraint violation in the objective function. In this study, the gradient projection (GP) algorithm was adapted. RESULTS : Two numerical experiments were conducted to demonstrate the features of the soft capacity constraint model and the computational performance of the solution algorithm. The results revealed that imposing the soft link capacity constraints can ensure convergence. CONCLUSIONS : The proposed model can be easily extended by considering other traffic assignment models, for e.g., non-additive traffic equilibrium problem, stochastic traffic equilibrium model, and, elastic demand traffic equilibrium problem. Furthermore, the model can exist regardless of the sufficient capacity for each O-D pair to cater to their demands.

PURPOSES : This study verifies the stability and uniqueness of the traffic assignment algorithm. METHODS : The traffic assignment step of the four-phase traffic demand model is an important step in determining the traffic volume of the link in the process of distributing the O/D traffic volume on each link. In this step, primarily, a link-based algorithm based on user equilibrium has been used. The typical link-based algorithm, FWA, is known to provide uniqueness and stability, in theory, regarding traffic assignment results. However, recent studies have raised the controversy that, in reality, the FWA is less stable and unique depending on the termination criterion applied to the FWA in the traffic assignment step. Stability tests and proportionality tests were conducted for the application of algorithms to widely used commercial software (for example, EMME, CUBE, and TransCAD). RESULTS : According to this study, the uniqueness and stability of the FWA were not followed in the process of actual traffic assignment, unlike the theory. CONCLUSIONS : The traffic assignment model has essentially the same result when the optimum level is reached, irrespective of the program and traffic allocation techniques used. Therefore, efforts will be required to recognize limitations in practice and to produce stable results at an appropriate level when predicting traffic demand, traffic volume, benefits, and feasibility studies using a traffic allocation model.

본 연구는 도시교통수요예측에 있어 비신호교차로 지체를 다루고 있다. 본 연구의 목적은 비신호교차로 지체식을 개발하고, 이 지체식의 적용결과를 비교분석하는데 있다. 이를 위해 이 연구에서는 한국도로용량편람(KHCS)에 의한 시뮬레이션과 EMME/2를 이용한 청주시 사례연구에 중점을 두고 있다. 주요 연구결과는 다음과 같다. 첫째, 총 480회의 시뮬레이션을 통해 통계적으로 유의한 8개의 지체식이 개발되었다. 둘째, 비신호교차로의 지체식을 적용한 추정치가 관측 교통량 자료에 가장 적합한 것으로 분석되었다.