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Once-only button pushers get green light

Dr Karl has been leaning on a lamp post wondering why, in our up-to-the-minute, fully-downloadable world, we aren't prepared to wait for anything?

We all spend time waiting for a lift to arrive, or waiting as a pedestrian to cross the road at the traffic lights. There's always somebody who will try to speed things along by jabbing their finger on the button over and over.

These people wrongly think that the more often and more vigorously they press the button, the quicker the elevator or walk light will appear. They're wrong.

There are several different types of control circuits to manage traffic lights.

Some traffic lights have no external detectors or press buttons at all, because they're in a large city where there's constant traffic day and night. These traffic lights simply work on timers.

But in areas where the traffic is less, such as in the suburbs or on country roads, a combination of control box, car detectors and input switches is used.

The control box has timers, processing circuitry and relays.

The car detectors can be anything from rubber hoses full of air to super-sensitive lasers. But the most common detection technique today is the inductive loop, coils of wire embedded in the surface of the road.

When a car (which has a lot of metal in it) rolls over these coils of wire, it becomes part of the circuit, which then tells the control box that a car has arrived at the lights.

(By the way, some very small motorbikes don't have enough metal to set off the more insensitive inductive loops, which is why you sometimes see the rider jumping off and pressing the walk button.)

The walk button is the most common input switch. But most city traffic lights can accept an override command from the control centre. For example, to give a continuous set of green lights for ambulances, fire trucks or VIPs.

You've probably noticed that when you press the walk button sometimes the lights change almost immediately, while at other times there's a delay of a few minutes.

The long delays usually happen in rush hour when you (the pedestrian) want to stop the road traffic, so that you can cross the road.

The rationale behind this decision is that it is better to keep one person waiting (that's you) rather than hundreds (that's the road traffic trying to get in or out of town).

But the important thing is this it takes only one stab of your finger on a button to set the process going. You can press it once or you can press 100 times. It doesn't make any difference to the control circuit.

It's exactly the same with the call button on an elevator. One single press is all you need.

In the UK, there used to be a system that counted the number of times that a pedestrian pushes the button. It used this information to regulate pedestrian waiting time. But it was discontinued.

In New York, the traffic lights are increasingly being controlled by computers. So the buttons are becoming obsolete. Fewer than 20 per cent of the buttons feed signals to the control boxes. The remaining 80 per cent are empty props.

In downtown Sydney, the buttons have no effect between 7am and 7pm, Monday to Wednesday; and 7am to 9pm, Thursday to Saturday.

However, they do work outside these hours, including all day Sunday. The rationale is that between these busy hours, road traffic is relatively constant, and the crossings are always being used.

But Harold Scruby, the executive director of the Pedestrian Council of Australia, said that "the pedestrian phases were too short, and that handicapped and elderly people found crossing the road before the red man appeared to be impossible".

In general, people vastly over-estimate the amount of time they spend waiting at traffic lights and elevators. Even if the wait is just 60 seconds, it feels like minutes.

Of course, if you're a fan of conspiracy theories, some people claim that the buttons are just there to trick the ignorant and taunt the wise, and have no effect at all and are not even wired into the circuit.

They are convinced that the green light or the elevator always follow the timing program and turn up when the control program dictates.

They reckon that these buttons are just a modern mechanical placebo, designed to placate the hyperactive people in our society.

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