Traffic lights don't work. I'm a pedestrian, cyclist and occasional driver, so am a user of lots of traffic lights, and they don't work. Their general usefulness has been called into question, and their "user interface" (UI) is non-intuitive. Almost any traffic light junction you visit will demonstrate that they just don't work properly, it at all.
Firstly, let's consider traffic lights in general. That basically covers lights at junctions and pedestrian crossings. We've all driven down streets and been stopped at what seems like every set of lights, often when there's no other traffic or pedestrians around. As Del Amitri sang, "the traffic lights change to stop, when there's nothing to go".
A few years ago, a chap called Hans Monderman realised that trying to make all road users 'automatons' wasn't the best approach. Instead, he realised that if everyone was required to make their own decisions, and take responsibility for themselves then actually everyone would benefit. He call this concept "shared space". Essentially, everyone gets to use the road, and has to avoid everyone else.
We can't very well mention traffic lights without mentioning cyclists who jump the lights. It turns out men do this more than women, and because of that, women are more likely to die at at traffic lights by being crushed by an HGV. Aside from some very clueless cyclists who assume any space is a good space, don't understand how vehicles move and how drivers see, this sort of news is unlikely to quell the tides of cyclists that routinely skip the lights.
So much for the concept of traffic lights in general. We're a long way from getting rid of them, so while we've got them, we ought to find ways to get along with them. Here's where my next point, the "user experience" is completely wrong.
As pedestrians, we've all been taught from a young age that when you want to cross at the lights, you press the button and wait for the "green man" (who tends to be white in North America). Obviously, if you see a red man, then you wait.
As a kid, traffic lights were called Pelican Crossings. These particular junctions had a "flashing green man" stage, which indicated to pedestrians that the "red man" was coming, which would mean the traffic would want to start moving again. The road traffic would see "red" whilst the "green man" was on, and a flashing amber light around the time that the "flashing green man" was on. This flashing amber light denoting "you can go, if it's clear".
A number of UK councils have stopped installing Pelican Crossings and now use Puffin Crossings instead. Puffin Crossings use infra-red sensors to detect pedestrians, so keep the "green man" on while pedestrians are crossing. As soon as they're all gone, then it turns to "red man" and lets the traffic go, following a "red, red+amber, green" sequence. Haringey Council has a "guide to Puffin Crossings", which looks horribly complicated, and is sadly only available as a PDF. Newcastle's got a bit more information about the different types of crossing.
I can't find any decent reference about them, but a lot of lights seem to be a mixture of Pelican and Puffin - that is, they seem to have dropped the "flashing green man" stage in favour of no pedestrian light at all. Also, a lot of lights that used to only operate on half of the road seem to have been replaced with a single light for crossing the whole street in one go.
Here's where my "user experience" gripes come in. Firstly, the "no light" stage for pedestrians seems to be universally confusing. It's not really obvious if there's no working light, or if one should wait rather than cross, or perhaps one can hurry over and be okay. I guess here in the UK we're used to the idea of stuff not working, so the "oh, it's a broken light" response seems to be prevalent, especially as you can probably see some people apparently crossing the road, and the traffic dutifully waiting.
Having a "red man" when only half of the road has traffic on it is also confusing if there's a pedestrian island. If there's no island then it's pretty obvious what's going on. However, if you can see a "red man", but no traffic on "your part of the road" then should you cross? It's completely unclear what to do, and seems to confuse a lot of people.
So to recap... The validity of even having lights all over the place is in some question. Then we don't apparently understand the actual sequence of lights we see, because we all suspect that something's not working quite right because either the light is broken, or else it's perfectly okay to cross since other people are doing it. Then we've got cyclists jumping the lights as if they've been shown a green signal, and you've got a whole load of very confused pedestrians.
What ever's going on, one thing is clear: Traffic lights don't work.