PURPOSES : The purpose of this study is to review a method to estimate the average travel speed of the Bus Rapid Transit(BRT) section using the bus departure and arrival time data collected using the Korean bus information system (BIS). METHODS : To determine an average travel speed estimation model suitable for the BRT system in Korea, the speed estimated using the speed estimation model of TCQSM, which is used in the U.S., and that using the proposed speed estimation model that used the bus departure and arrival time data were compared with the actual travel speed using a t-test. RESULTS : The average travel speed estimated using the proposed method was more suitable for the actual average travel speed than that estimated using the TCQSM model. CONCLUSIONS : As a result of estimating the average travel speed, if the length of the link is 900 m, SBRT can be constructed on the existing road, but at least 1,200 m must be ensured to build SBRT in the new city. The proposed bus average travel speed estimation model can be used to review the BRT operational efficiency considering the speed limit, traffic signal, and dwelling time at bus stops in the planning and operation stages of the BRT.

PURPOSES : There are generally various driving behaviors in toll collection areas, including lane changing, merging and diverging, and other behaviors. Because of these behaviors, accident risk and traffic congestion may occur. To mitigate these problems, multi-lane electronic toll collection systems have been developed with a high-speed limit of 80 km/h. This study was conducted to investigate travel speed changes and effects through multi-lane electronic toll collection systems with a high-speed limit. METHODS : Traffic simulations were conducted using VISSIM. Before conducting simulations, driving behavior around the toll collection areas was observed, and field data were collected based on drones for peak and non-peak hours. In addition, safety effect evaluations were conducted based on conflict analyses using the SSAM software. RESULTS : Through multi-lane electronic toll collection systems with a high-speed limit, the travel speed on the toll collection area was increased, and traffic operational efficiencies were identified. However, different speed variations were produced as observation locations in toll collection areas. Speed variations were mitigated at most locations except the area within the tollbooth because of the high speed limit for multi-lane electronic tollbooth. CONCLUSIONS : It was important to manage lane-changing activities, and this may influence traffic operational effects. Safety effects were also identified through conflict analyses.

PURPOSES : The purpose of this study is to build an optimization model using the capacity and initial travel speed of the volume delay functions for network calibration performed in the traffic demand analysis process. METHODS : The optimization model contains an error term between the observed traffic volume and estimated traffic volume, based on the user equilibrium principle, and was constructed as a bi-level model by applying range constraints on capacity and travel time. In addition, we searched the split section to apply the method of adjusting the section instead of adjusting the single link. The optimization model is constructed by applying the warm-start method using the bush of the origin-based model so that parameter adjustment and traffic assignment are repeatedly executed within the model and the convergence of the model configured %RSSE. RESULTS : As a result of analysis using the toy network, the optimization model is that the observed traffic volume is estimated when there are no restrictions and, when the constraint conditions were set, the error with the observed traffic volume and error rate was significantly reduced. As a result of the comparative analysis of the trial-and-error methods, KTDB optimum values, and optimization models in empirical analysis using a large-scale network, the evaluation indexes (e.g., RMSE and %RMSE) were significantly improved by applying the optimization model. CONCLUSIONS : Based on the empirical analysis, the optimization model of this study can be applied to large-scale networks and it is expected that the efficiency and reliability of road network calibration will be improved by repeatedly performing parameter adjustment and traffic assignment within the model.

PURPOSES : The purpose of this study is to identify the factors affecting the effectiveness of speed limit change that is defined as the amount of increased travel speed. METHODS: A ordered logit model was adopted to analyze the relationship between the change in travel speed and contributing factors. A stretch of Kyungbu freeway was selected for the analysis because the Korea expressway corporation has raised speed limit from 100km/h to 110km/h since September 1st in 2010. RESULTS: The results showed that geometric design elements, speeding cameras, and section length were identified as factors contributing the effectiveness. Contributing geometric design elements include the number of horizontal curves and vertical curves that do not meet the design requirement with 110km/h speed limit. CONCLUSIONS: The outcome of this study will be used for establishing various traffic operations and control strategies for freeway speed management.

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.

PURPOSES : Adverse weather conditions such as heavy rain, heavy snowfall, and thick fog and so on have highly affect on the change in traffic conditions on the road. In particular, heavy snowfall causes capacity reduction as well as crash occurrence. This study investigated the effects of snowfall on speed on a freeway. METHODS : Vehicle detection systems data were matched with corresponding weather station data by regression analysis. RESULTS : The results show that the travel speed is reduced by 6.7% under little snowfall and by 12.8% under heavy snowfall. Regarding the speed variation, 8.7% and 114.7% increases are observed under little snowfall and heavy snowfall, respectively. It is also found that 1 cm increase in snowfall leads to 0.4% decrease in travel speed. In addition, the travel speed increases by 0.4% when the temperature increases by 1℃. CONCLUSIONS : It is expected that the outcome of this study will be useful in establishing more effective strategies for winter operations and road maintenance in practice.