Canada

The effects aren't instant but over a longer period of time cameras have proven to slow down traffic leading up to the camera and after the camera, many streets still see a drop in average speed after the camera is removed. The main benefit is the cost of operating the cameras is quite a bit cheaper than paying a cop to do it.

My area operated 6 cameras for 1 year for a cost of about 323k. Given those cameras took no days off, took no coffee breaks, and has no downtime while writing a ticket, i doubt they could have covered the same area and timeframe with 10x the cost running officers and their cars.

The camera can also watch its road 24/7 as long as it is deployed. The camera cant be racist, can't rip up a ticket due to bribes or cleavage, and can't give special treatment to their buddies. Most places won't let you dispute the camera ticket whereas many speeding tickets sent to court see fines reduced and also clog up court house time, often taking the cop off duty to recall the events.

The cameras are not perfect but traffic fatalities/injuries and the attitude towards speeding in this province is so out of control I'll take a not perfect solution over no solution.