Lots of people don't bother to press the button at pedestrian crossings. Do they know something the rest of us don't?
It can seem like the longest two minutes of your life. You get to a road junction just as the red man appears.
If it's a busy junction, anywhere in the UK, you might see people who don't bother pressing. Ask them and they'll tell you it doesn't do anything.
It's not an absurd theory. In New York, they are sometimes referred to as "placebo buttons" as in many locations they appear to have no effect.
But in the UK does pushing the button make any difference?
The short answer is - it depends. At a standalone pedestrian crossing, unconnected to a junction, the button will turn a traffic light red.
At a junction it is more complicated.
Take one very busy crossing - at the intersection between Regent Street and Cavendish Place, near the BBC's HQ in London - and you immediately start to doubt the button's efficacy.
Sometimes people press it, sometimes they don't. In both cases there is a 105-second interval between the red man coming on and the green man appearing.
This is mid-afternoon. In the morning it is slightly longer - 110 seconds.
At night, the button does act to stop the traffic, says Transport for London. But this is only between the hours of midnight and 07:00. In the daytime, the button has no effect.
It's not just in the capital. The UK uses a traffic system called Scoot (Split Cycle Offset Optimisation Technique) so the same overall principles apply whatever town or city you live in.
Edinburgh has roughly 300 traffic junctions of which about 50-60 are junctions where the green man comes on automatically. In the jargon this is known as "walk with". It is usually where a one-way street connects with another road. The green man comes on whenever the red traffic light shows. At night this might change but during busy times the system is automated.
In Manchester, around 40% of the push buttons don't need to be pressed during busy pedestrian times. "This is made up of those pedestrian green men that are 'walk-with-traffic', and those set remotely on a timer from our central computer," a Transport for Greater Manchester spokeswoman says. "The times vary depending on the junction but the maximum wait time is 60 seconds."
The details may vary but a similar system operates in Cardiff and Glasgow.
Traffic junctions can be divided into two main types. Those where all vehicle traffic is stopped at once for the pedestrians. And those where part of the junction is stopped for pedestrians while on the other half, motorised traffic gets a green light.
At the first type, such as the busy Oxford Circus junction in central London where two main roads intersect, it is always necessary for a pedestrian to press the button in order to get a green man. If they do not, the traffic lights will miss out the pedestrian phase of the cycle and simply alternate between giving a green light to each road.
The time that a traffic light stays green for is influenced by sensors in or above the road, which tell the traffic system whether cars are waiting. If there are no vehicles waiting at a side street, the main road will get a continuous green.
A cynic might argue the button is occasionally there merely to give the pedestrian the illusion of control. So are they misleading people?
"It could be interpreted in that way," says Anna Collins, policy lead for pedestrian crossings at campaign group Living Streets. On the other hand, having push buttons at every light brings consistency. It reinforces the message that it may be better to wait for the green man than charge out into the traffic, she says.
The philosopher Julian Baggini says it's demeaning being misled even on something so seemingly trivial. "We want to be treated as intelligent, autonomous agents rather than being manipulated."
Transport for London denies it is misleading people. There are 4,650 pedestrian crossings in London of which about 2,500 are at junctions. At the majority of these junctions the button controls the green man, says Iain Blackmore, Head of Traffic Infrastructure at TfL. It is difficult to say how many are completely automated and how many operated by the button without someone analysing each junction, he says.
Outside London, the decision for programming crossings is for the local authority. A Department for Transport spokeswoman says that at busy junctions "the pedestrian crossing may be programmed to come up every time even if no-one presses the button".
Sometimes the reasons for a non-responsive button are not traffic-related. In 2012 TfL changed the pedestrian setting at Henlys Corner in north London after discussions with the Jewish community.
Orthodox Jews are not allowed to operate electronic machinery on the Sabbath. The change means that from sundown on Friday to sundown on Saturday the pedestrian crossing operates on an automated programme rather than via pressing the button.
The maximum wait time for a green man in the UK is set at two minutes, says Martin Low, transport commissioner for Westminster City Council.
That can feel like a long time.
Low wants councils to help pedestrians to cross even if there is a red man. Instead of constructing barriers, Westminster is putting in "perch" islands in the middle of roads to allow pedestrians to get across.
And here is where the UK differs from some other countries. The British pedestrian looks to cross whatever the lights, merely checking whether any traffic is approaching. (The law is on the pedestrian's side, except on motorways, certain other roads, and, although not usually enforced, in Northern Ireland.)
In Washington DC, say, this behaviour would be seen as at best daring and at worst an example of illegal jaywalking. The British historian Felipe Fernandez-Armesto was arrested in Atlanta for jaywalking after crossing at the wrong place.
In some north European countries, it is against the law. In others, merely likely to raise eyebrows.
This is about safety not just convenience, says Benjamin Heydecker, professor of transport studies at University College London. There might be a case for bringing in a jaywalking law in the UK, he argues.
Low says it's a "terrible" idea. He believes in the individual's right to choose when it's safe.
"If it's a red man but safe to cross you should let someone. We need to get away from the traffic management approaches of the past like putting guard rails everywhere."
There's no need to remove buttons, says Baggini. But a little more honesty about what they do would be nice. "Traffic planners don't need to mislead us. They can just honestly say, look, all pedestrian crossings have buttons because that makes it easier. Some do nothing, but believe us, your urban pedestrian travel experience would be worse without them."
Here is a selection comments on Facebook.
It happens all the time. I come to lights and check the button which has not been pressed but there are 10 or more people waiting. Unbelievable.
I hate it when I want to cross the road and people already waiting haven't pushed the button. Some junctions are on a cycle, yes, but most junctions won't stop traffic to let pedestrians cross if it hasn't been informed there are pedestrians waiting. The system isn't magic, it works on an input/output basis like any other.
They work in not so busy places such as round the corner from my house - absolutely love watching people standing there wondering why the lights won't change!!!!
In my experience - it's quicker just waiting for a break in the traffic.
It drives me mad when people cross on the red man, esp. in front on little kids (eg mine!) Kids see an adult cross so assume it is safe to do the same.
What annoys me most is, when someone presses the button when the road is clear, then walks across the road anyway, then the lights turn to red as my bus is approaching and there is nobody at the crossing!
As a commuting cyclist I find it even more annoying when people DO press the button but then immediately proceed to walk on red anyway. Almost daily I witness this and other road users then have to wait at that crossing for no reason 2 minutes later. Unless the button has a more or less immediate effect I think it's totally pointless putting them there as most people have walked off by the time the lights do change. Moreover, if I took the same approach as most pedestrians and crossed on red on my bike because no one is there and I decided it is safe to do so, I would still get fined, but the pedestrian, having committed the same "crime" would not. Fair? I think not!
I am a convicted Jaywalker in Northern Ireland, so it is enforced. (who knew). £250 fine and a criminal record.
I try not to press it so as to not inconvenience motorists. I either wait till no motorists are about or are far away. And if I do, it is only if the traffic is constantly busy.
I never press it as by the time it comes on I have always crossed safely and then it holds up the traffic with no one crossing. Some inconsiderate people press it and don't wait for green man which is a big bug bear of mine.
I always press it but make a judgement when to cross - there's few things more peculiar than watching a pedestrian wait for the lights to change when the streets are clear.
It certainly varies around the world. In the UAE I don't recall there being any buttons to press. The cycles are fixed and 24/7. In Hong Kong they are fixed, but have the help thing for the impaired. What is neat is you get an audible warning, like a tapping. Slow on the red, fast on the green and intermediate as the green cycle runs out. Escalators have a similar neat system, rather like a peg on a bike wheel, with a different speed at the start of the escalator to that at the end. And some places have a whole intersection cycle so you can cross diagonally at one go.
Timers next to the green man to let you know how long you've got are being introduced in Plymouth and its a good idea!
Some clever traffic engineer should design some more intelligent traffic lights - the dumb timer-based logic on most automated pedestrian crossings is not always safe for children/elderly and the blind, and often leaves traffic waiting needlessly after braver pedestrians have already crossed. A better system could use motion detectors/radar to determine when lights should change and for how long.