Racing AI Revisited: Box Collider Trigger vs Raycast vs ??? - Performance

I've so far managed to improve the (now defunct) Gotow Car tutorial to use adjustable waypoints that can slide along the track width. The next step is to add collision avoidance for vehicles.

In terms of performance, which is a better approach - two box-colliders surrounding each vehicle along perpendicular axes, or a series of raycasts that extend along different angles from the front of the vehicle?

 

Box colliders are better in terms of performance. Keep in mind that Mesh colliders are not that good as box colliders.