Examining the feasibility of current spiral curve design controls for LiDAR-based automated vehicles

Abstract

Enabling large-scale deployment of automated vehicles (AVs) in the near future requires answering the question firstly: whether AVs could safely adapt to as-built road geometry? This study aims to examine the feasibility of current spiral curve design controls for LiDAR-based AVs (LAVs) from the perspective of the available sight distance (ASD). A series of tests featuring the design speed (Vd), lengths of tangent (LT) and spiral (LS), circular curve radii (R), and point thresholds for detection (NT) were simulated in PreScan/MATLAB/Simulink co-simulation platform. The ASDs affected by those parameters’ combined effects were analyzed and compared with required stopping sight distances (RSDs) of human-driven vehicles (HVs) and level 3 to 5 (L3–L5) LAVs followed by proposing the ASD-oriented safe speeds and the corresponding speed limits. The results indicate that: (1) the combination of the tangent-spiral curve-circular curve causes a shorter ASD than that without the spiral curve; (2) a longer spiral curve causes a shorter ASD; and (3) only a low-type combination of R, LS, Vd conditions is feasible for L3 LAVs while L4 or L5 LAVs have difficulties in dealing with high-type conditions. These findings help understand the ASD for AVs and provide safety-critical speed references for administrators.