The supply of highway facilities in urban and suburban areas across South Korea has not kept pace with automobile growth, resulting in traffic congestion, and congested roads have contributed to worsen operation and safety problems with high fuel consumption. Traffic agencies and engineers in South Korea have focused on mitigating congestions through Intelligent Transportation Systems (ITS), demand managements, and other conventional measures. Unfortunately, these conventional countermeasures were exhausted in Korea to mitigate traffic congestion. From the viewpoint of efficiency and safety, a superstreet might be one of the alternatives to be considered for solving traffic problems. A superstreet is an unconventional intersection which redirects left turn and through movements from side streets. The design concept leads to increase safety by reducing conflict points at a major crossing point and operating like a pair of one-way streets which signals independently control from the both directions. Prior research have reviewed the performance of the implemented superstreets in North Carolina, U.S and showed a significant improvement in operation and safety compared to existing conventional intersection designs. The purpose of this paper is to provide insight on the potential to implement a superstreet as a promising solution for improving mobility and safety in the South Korea. This paper evaluated how a superstreet design effectively and safely handles with given traffic circumstances compared to an existing design. The VISSIM Model was selected to simulate the operations of subject intersections and Surrogate Safety Assessment Model (SSAM), developed by Federal Highway Administration (FHWA), which performs conflict analysis by processing vehicles trajectory data extracted from micro-simulations, was adopted to evaluate safety estimations. The results showed that the corridor with superstreets have the most effective progression of traffic along the entire road section with the fewest stops and lowest delays. Also it indicated that superstreets would contribute to have a decrease in collisions. The results would suffice to provide traffic agencies and engineers with an effective alternative to improve safety while reducing congestion.

A dynamic offset with coordinated signal control system (DYCCS) was developed in this study. When configuring the DYCCS, the Critical Intersection (CI) of a coordinated corridor was operated based on saturation equalization signal control, and the adjacent intersections were controlled by coordinated semi-actuated signal control, with the background cycle corresponding to the suggested cycle length of the CI. An algorithm for the dynamic offset was suggested to integrate in the coordinated semi-actuated signal control algorithm and the saturation equalization signal control algorithm. Moreover, simulations were conducted for pre-timed signal control using one or three optimized signal timings and the DYCCS. The simulations demonstrated that the DYCCS can decrease the average vehicle delay relative to an optimized time of day and a Coordinated Signal Control System (CCS) utilizing a fixed offset. It is anticipated that the implementation of this DYCCS in newly constructed intersections or existing intersections controlled by a pretimed signal control may significantly decrease vehicle delay and may enhance progression effects in a coordinated corridor. A local controller equipped with this algorithm combined with an existing traffic responsive control, such as COSMOS, would be efficient under various conditions.

The operational efficacy of lane departure warning systems (LDWS) in autonomous vehicles is critically influenced by the retro-reflectivity of road markings, which varies with environmental wear and weather conditions. This study investigated how changes in road marking retro-reflectivity, due to factors such as weather and physical wear, impact the performance of LDWS. The study was conducted at the Yeoncheon SOC Demonstration Research Center, where various weather scenarios, including rainfall and transitions between day and night lighting, were simulated. We applied controlled wear to white, yellow, and blue road markings and measured their retro-reflectivity at multiple stages of degradation. Our methods included rigorous testing of the LDWS’s recognition rates under these diverse environmental conditions. Our results showed that higher retro-reflectivity levels significantly improve the detection capability of LDWS, particularly in adverse weather conditions. Additionally, the study led to the development of a simulation framework for analyzing the cost-effectiveness of road marking maintenance strategies. This framework aims to align maintenance costs with the safety requirements of autonomous vehicles. The findings highlight the need for revising current road marking guidelines to accommodate the advanced sensor-based needs of autonomous driving systems. By enhancing retro-reflectivity standards, the study suggests a path towards optimizing road safety in the age of autonomous vehicles.

In this study, the traffic operational effects of a pacemaker system (PMS) on the traffic operation in the Geumnam Tunnel on the Seoul–Yangyang Expressway was evaluated herein using a before–after analysis based on long-term vehicle detection system (VDS) data. Changes in spatiotemporal traffic flow and traffic capacity, and speed improvement under different levels of service (LOS) were analyzed using data from five VDS detectors installed upstream and downstream of the tunnel. After PMS installation, (i) increased average and 25th-percentile speeds at most detector locations and decreased standard deviation of speed were observed both near the tunnel exit and the downstream sections, (ii) maximum traffic volume was increased from 1661 to 1765 veh/h/lane (~6.3% increase), (iii) LOS-based speed improvement analysis showed that mean speed and 25th-percentile speed increased by ~6.5%, indicating the alleviation of speed reduction among low-speed vehicles due to PMS. These results prove that PMS increases vehicle speed, reduces speed variability, and enhances traffic flow stability and processing capability. These findings provide empirical evidence supporting the operational effectiveness of a PMS as a practical tool for mitigating phantom congestion in highway tunnel sections and reducing the speed differences between vehicles and improve traffic stream stability.