I tweeted a little clip of something from a commute of a few months ago. It was the police making a couple of annoying, potentially very dangerous, and entirely understandable mistakes.
First, the police driver has blocked an advance stop box. I imagine probably the lights were green when they entered it, but a traffic jam ahead of them prevented them continuing on their way before the lights turned red.
It’s a common problem. Blocking ASLs is the least of it. Blocking pedestrian crossings and entire junctions happens all the time too, because motorists know they can try their luck and just keep bumper hugging in slow-moving traffic without worrying about whether they’ll be able to see when the lights turn green again. Aggressive motorists can nudge forward through red lights and pedestrian crossings, ready to floor it when they see their light turn green.
My thesis is that this behaviour is not merely accommodated by repeater traffic lights on the far side of junctions, but over time it has been slowly, creepingly encouraged by it. Those who have driven or cycled outside the UK will have noticed that having multiple signal heads to display the same signal strewn about a junction are quite a British peculiarity. They’re not unheard of elsewhere, but it’s far more normal to have just the one signal — in most countries, always situated at the stop line (but in some, always situated directly opposite on the far side of the junction).
And they exist purely to accommodate drivers who have overshot their stop line. I guess at some time, somebody identified that there was a niche problem: occasionally a driver accidentally stopped over the line, or had to make an emergency stop for some reason, and then couldn’t see when lights changed. And they invented far-side repeaters as a solution, and in doing so have created a far more ubiquitous and pernicious problem.