This analysis doesn't say whether minority drivers were more likely to be pulled over for traffic violations, only that they were more likely to be issued a cit

This analysis doesn't say whether minority drivers were more likely to be pulled over for traffic violations, only that they were more likely to be issued a citation and that those citations came with higher fines. I would guess a cop rarely knows the race of a speeding driver before pulling them over. The discrimination would happen either when deciding whether to issue a citation, or after looking up the driver's info on the police car. When the police look up your info, do they see past citations? If so, it's a self-reinforcing cycle: people more likely to receive citations are more likely to have citations listed, and a cop who sees past citations might be less willing to let the driver off with a warning.