Investigation on lane operation restriction (LOR) policy at on-ramp junctions

On-ramp-freeway junctions are subject to vehicle interactions merging between mainline and ramp flows. The turbulence created by these interactions often causes local congestion, and can lead to breakdown in cases where the total arriving ramp and freeway flow exceed the capacity of the downstream freeway segment.; This paper discusses a freeway control policy of a new approach—the lane operation restriction (LOR) policy. LOR policy focuses on traffic operation improvements at on-ramp junctions with relatively high ramp flow rates. LOR policy intends not only to control ramp flow progressions and movements in the ramp influence areas by traffic control devices such as barriers or painted markings, but also to induce appropriate lane distributions upstream by stimulating drivers' anticipation on the turbulence by ramp flow. It reduces flows in lane 1 immediately upstream and the turbulence with ramp flow in the ramp influence area.; Principles of LOR policy are consistent with empirical findings at on-ramp junctions. Breakdown and congestion spread across all lanes when the flow of lane 1, which is closely related with ramp flow, is suddenly increased to near capacity. Lanes 2 and 3 show a higher density-speed relationship than lane 1. Downstream of ramp influence areas show comparatively higher speed at the same density, or higher density at same speed, than upstream of ramp influence areas. Therefore, vehicle shifts from lane 1 to lanes 2 and 3, through LOR policy, can significantly affect traffic operations in the vicinity of on-ramp junctions.; In this study, three types of barriers (A, B, C) are analyzed using a simulation approach. They show potential operational improvement in network wide area as well as in the vicinity of on-ramp junctions. More traffic improvements from LOR policy are noted as a result of lane distribution control of flow upstream of ramp influence areas, rather than those resulting from directly restricting progression and movements of ramp flow in ramp influence areas. The combination of both control factors, type B, maximizes traffic improvements resulting from LOR policy.