It could be. I lack the data at the moment but I seem to remember when deaths were higher 20 years ago (3400 a year vs 1700), exceeding the speed limit was high

It could be. I lack the data at the moment but I seem to remember when deaths were higher 20 years ago (3400 a year vs 1700), exceeding the speed limit was higher in the causes. What cameras may have done is change the culture of speeding, making it far more antisocial - like the drunk driving campaigns did. If others don’t speed, then you generally can’t speed, especially in towns where it’s most dangerous. My parents used to speed all over the place in the 90s, my peers don’t today. Perhaps the cameras don’t make any local difference, but are part of a larger cultural shift. More people are killed by car drivers knocking down pedestrians than by car drivers speeding.