Today I learned sth in here about unity.
Confused me, but seems legit.
(Your question made me to quest the following post)
If you got a trigger, you got a collider.
In your case one collider is that “wall”.
I assume that rigidbody is the car (player) .
So: Does your player use “discrete” or “continous” collosion-detecting?
I hope for a win-win-situation.
Your problem solved. My question answered. 
Thx
Chris