Yes. As soon as the automated traffic enforcement purpose is done with (the car wasn't speeding/wasn't running a red/so on) the data should be deleted.
If the police reach the data before it's deleted after they know it may have evidence of a crime that's ok (realistically this is rare, but I can imagine it happening with paired cameras that measure speed over a long distance of road. You could also get lucky where a false positive image happened to capture a different crime), but we shouldn't be storing surveillance data that tracks everyone's movements on the off chance that it has evidence of a crime. The harm outweighs the use at that point.
If the police reach the data before it's deleted after they know it may have evidence of a crime that's ok (realistically this is rare, but I can imagine it happening with paired cameras that measure speed over a long distance of road. You could also get lucky where a false positive image happened to capture a different crime), but we shouldn't be storing surveillance data that tracks everyone's movements on the off chance that it has evidence of a crime. The harm outweighs the use at that point.