There are seven pedestrian crossings at the Bow Roundabout.
All of them have buttons, but only three are worth pressing.
This one's worthwhile.
This is the crossing at the entrance to Bow Road. I took this photo coming home from the supermarket yesterday. You have to press the button or the traffic feeding off the roundabout never stops. Sometimes the traffic's quiet enough that you can dash across but if you want to play it safe the button is essential. It always stops the traffic at the same point in the cycle, just as the northbound A12 sliproad gets the green light, and the button always works.
However this one's useless.
This is the crossing at the exit from Bow Road alongside the McDonald's drive-through. I took this photo coming home from the supermarket yesterday. It has a button but there is absolutely no point in pressing it - the traffic stops anyway and it doesn't speed things up.
This one's useless too.
This is the crossing underneath the Bow Flyover leading to the centre of the roundabout. It has a button but there is absolutely no point in pressing it - the traffic stops anyway and it doesn't speed things up.
And what's interesting is that people generally don't realise this and press the buttons anyway. Parents heading to the shops press the buttons. Worshippers off to the mosque press the buttons. Children on their way to school press the buttons. This is despite the fact that many of these people use the crossings regularly and the buttons have been pointless for almost ten years.
These are the seven crossings, shown in yellow.
The three with useful buttons have a ✔.
The four with useless buttons have a ✘.
The difference is all down to whether the pedestrian crossings are at traffic lights or not. The four ✘s are at lights which control traffic on the roundabout. Cars and vehicles stop here anyway, and pedestrians simply cross the road while traffic's being held at red. The three ✔s are at additional crossings which had to be added to ensure pedestrian flow across the interchange was possible. Cars and vehicles only stop here if pedestrians request it, potentially slowing traffic in the vicinity of the roundabout.
And pedestrians generally don't realise any of this, why would they? I know because it's my local roundabout and I've used these crossings many hundreds of times since 2015. I know because the phasing of the lights at the Bow Roundabout never varies - the cycle's always 64 seconds long and a mere pedestrian cannot speed things up. I know because I'm observant and I like analysing systems. I know not to press the four duff buttons, only the three useful ones, but I am very much in the minority.
London contains many types of button-operated pedestrian crossing but they all boil down to one of two types - those where the button stops the traffic and those where the traffic was always going to stop anyway. The Bow Roundabout has both.
In the latter case what the button often does is speed up how quickly the traffic stops, which effectively creates a third category.
DON'T PRESS - TRAFFIC WON'T STOP
PRESS - TRAFFIC MIGHT STOP QUICKER
PRESS - MAKES NO DIFFERENCE
London is full of type 1 and type 2 crossings, those where pressing the button matters. These include pretty much every standalone pedestrian crossing and also those at the majority of traffic lights. But sprinkled inbetween are the pointless buttons, the ones you never needed to press but doing so probably made you feel more in control.
I've also found a really annoying type 3 variant, where the traffic stops anyway but the green man doesn't light up.
This is the junction of Prince Regent Lane with the A13 in Canning Town. There are multiple pedestrian crossings here, as befits a junction on a major arterial dual carriageway, but whoever programmed these lights did something particularly sly. The red man displays permanently, even while traffic is safely stopped at a red light, and you'll never see it turn green unless someone presses the button.
I timed the lights and it turns out traffic waits patiently here for a full minute waiting to exit Prince Regent Lane. But if a pedestrian turns up at any time during that minute they'll see a red man, not green, which is very much not what happens at any normal crossing. They could cross safely but won't discover this unless they press the button, and even then it doesn't change to green immediately by which time they could have been on the far side.
Not only is this wasting people's time unnecessarily it's also potentially dangerous. A lot of pedestrians use the change from green man to red man as a signal that they ought to hurry up and get across. If that change never happens and you decide to dash across on red, perhaps because the traffic hasn't moved in ages, you could all too easily be surprised when a car starts accelerating towards you. Other junctions on the A13 in Newham are like this too, as if the area's had its traffic lights programmed by sadists.
So keep an eye out if you're walking around town and attempting to cross a busy road at a pedestrian crossing. Sometimes that button has absolutely no effect, and other times you'll never see the green man unless you press it. Just occasionally we pedestrians are being played for fools.