The entire map need colliders in order for it to be a solid surface that cars can drive on. However, it would be horrible to just use mesh colliders for all of them, because some meshes are quite complex so they might drain performance quickly. Therefore, I fully separate every part of my map into two types:

• Visual mesh: for visual display of the mesh only (materials / shaders). Visual mesh is created first, then I make a copy of the visual mesh and simplify its shapes into boxes or simple shapes to be its collision mesh.
• Collision mesh: not visible, only for physics and colliders (mostly box colliders / mesh colliders for complex meshes); rigidbody if it is a movable object.

This was first iteration of test driving on the map which I was really excited about, after modelling the map for about a month. Although I was was quite happy about how the map looks, it was still important to evaluate on it from my first-hand driving experience on it, to make driving on the map an actually fantastic experience when navigating and traversing through different areas.

After driving around the map for a sufficiently long time, these are my markups on the map about how it can be improved. The main suggestions include:

• Adding 4 more entrances (1 on each side) to the Choi Hung Estate carpark.
• Amending the opening direction of the top-left school entrance.
• Adding a new alley between the west of Wet Market and the back of Fire Station.
• Adding a bridge to connect the highway to the second floor of Bus Terminal, to improve its ease of access.
• Expanding the area of the carpark on the second floor of Bus Terminal.
• Widening the widths of some entrances and alleys.
• Adding more alleys.

I'm going to edit the map accordingly and carry out the second iteration of the map design in the future.