In the US, speed limits are set far lower than required for safety, in order to maximize revenue from citations. More importantly, it allows the police to pick and choose who to pull over: When 99% of cars on the freeway are speeding, the police can pull over anyone, and they will use that discretion to pull over “certain kinds” of people they would like to target. Black people get pulled over less frequently at night, when the darkness does not allow the officer to see who is in the car they choose to pull over[1].

1: https://news.stanford.edu/stories/2020/05/veil-darkness-redu...