###### Abstract  
Given the rapid construction of freeways in developing countries such as China, land use is constantly under strict constraints, leading to challenges in adopting conventional layouts for interchanges. Implementing right-turn ramps on the left (RTRL) at interchanges can minimize land occupancy; however, the traffic safety level in this type of diversion area design requires extra attention. This study examines the decision sight distance for right-turn exit ramps on the left side. Utilizing unmanned aerial vehicle (UAV) video and the YOLOv3 target detection algorithm, the original trajectory data of vehicles in the diversion area is extracted. Employing Kalman filtering and Frenet coordinate system conversion reveals microscopic vehicle lane-change patterns, velocities, and time headways. Furthermore, the driving simulation experiment assesses driver behaviors in RTRL, with subjective, task performance, and physiological measure indicators. Ultimately, the range of the decision sight distance is defined, and establishing a calculation model involves determining relevant parameters based on measured data and simulation outcomes. The results indicate potential insufficiencies in the decision sight distance when standardized values are applied to RTRL. interchange; right-turn ramps on the left; decision sight distance; theoretical calculation; driver behavior simulation 2024 14 6205 10.3390/0000000-0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-00000-000000-00000-00000-00000-00000-000000-00000-000000-000000-000000-0000  
The innovative design of RTRL not only minimizes land usage but also circumvents the extensive demolition of surrounding buildings, thereby mitigating its impact on the environment. Furthermore, it addresses safety concerns arising from the convergence of small traffic streams exiting from the left-hand side of the right-turn ramp into the main traffic flow. Nonetheless, challenges persist in ensuring optimal traffic safety with this ramp-layout configuration. Firstly, RTRL is predominantly implemented in ramp continuous diversion areas, T- and Y-shaped interchange diversion areas, and mainline side continuous exit areas, but diversion areas have historically exhibited high accident rates [5]. Research indicates that 50% of traffic accidents occur during freeway exits, with the highest incidence observed at exit points compared to other interchange locations [6]. Secondly, driving behavior is closely related to road safety [7; 8; 9; 10; 11], with behaviors like straight-line driving and deceleration within the diversion area affecting exit traffic safety significantly [12]. RTRL innovatively challenges traditional design conventions by positioning right-turning vehicles from the left side in the forward direction. However, compared to conventional ramp layouts, this approach introduces greater complexity to road conditions with more signage. As a result, drivers may experience confusion during traffic, leading to reduced driving comfort, increased workload, and ultimately impacting traffic safety. Some scholars have evaluated the safety of exit ramps using actual accident data [13; 14; 15] or prediction methods to assess collision risk [16; 17; 18]. However, these approaches have not adequately considered interchange design aspects to enhance traffic safety in diversion areas. Safety within interchange diversion zones is influenced by various factors [19; 20], partly due to insufficient decision sight distance at exits, leading drivers to make emergency lane changes only when they are close to the exit. Some studies have proposed an identification sight distance calculation model by examining its practical application in freeway design in different countries [21]. Nevertheless, due to route alignment and structural limitations, controlling the exit-sight distance according to design standards or guidelines can be challenging in certain cases.