With less police on the road (or expected to perform 'normal' police duties, so not always interested in dealing with traffic offences), it's pretty much down to cameras to police junctions. I guess they can be effective for red light offences for some vehicles, and we know they love raking in the cash for blocking box junctions.
I guess people don't worry too much about being caught for jumping red lights, especially if they assume there's a factored in delay before the lights change in another direction (often there is, but not always).
Cyclists meanwhile see red as a give way or go throughout the red phase. Imagine if we ever saw motorists doing that. Perhaps you'll see some creeping over the stop line if the lights are red for some time, but never just deciding to go when the junction is clear.
I was surprised that buses would take the risk as they have cameras. Many commercial vans and lorries appear to be getting fitted with cameras now (I noticed recently that all Ocado vans have them), presumably to protect the company against claims - but, again, surely that would make drivers take more care?
I've got a dash cam now and it does make you conscious of the fact that footage could be used against you!