How do pelican crossings work?

[lavster]

can anyone tell me how a pelican crossing works? I've found loads on web about how traffic lights in generalbut I am interested in how the green man is generated one the pedestrian presses the button. is it a capacitor?

thanks :)

 

[mgb_phys]

They run on mains power.
The button starts a cycle of turning on the amber, then red lights for the drivers and the green light for pedestrians. You could do it with a simple 555timer and a counter but I suspect for reliability and to allow more complicated schemes, eg shorter delays at busier times, you would use a microcontroller.

 

[Danger]

What the hell is a 'pelican crossing'?
Is this another instance of Florida weirdness?

 

[DrGreg]

What the hell is a 'pelican crossing'?
Is this another instance of Florida weirdness?

It's the standard name in the UK for pedestrian-controlled traffic signals.

Pelican crossing.

 

[Danger]

Thanks for the clarification, Dr. Greg. That's some mighty weird terminology.
Here in Canada, a pedestrian crosswalk with a button has minimal effect. It causes the 'walk' light to illuminate upon the next normally scheduled switch of the main traffic lights. That points out to drivers the pedestrian right-of-way, which in normal traffic affects only someone turning onto the street in question (since someone already on that street is held up by the main lights). That right-of-way exists at all times, whether or not the intersection is lighted or even marked, but the light makes it more noteworthy.

 

[jtbell]

There are also midblock crossings that aren't associated with intersections, and are activated on demand by pedestrians.

 

[Danger]

There are also midblock crossings that aren't associated with intersections, and are activated on demand by pedestrians.

True. That's a relatively new development in my area. There are none in my town, but Calgary has quite a few.

 

[DrGreg]

There are also midblock crossings that aren't associated with intersections, and are activated on demand by pedestrians.

To clarify, that is what we call a "pelican crossing" in the UK. We have lots of them (usually in places a considerable distance from a light-controlled intersection). The lights at an intersection are just called "traffic lights" regardless of whether there's a pedestrian button or not.

One of the reasons "pelicans" have a special name is because the sequence of lights that the driver sees is slightly different: between red & green there is a flashing amber which means "give way to pedestrians, but otherwise, go".

 

[Danger]

I guess that I won't be renting a car if I ever visit England. Staying on the wrong side of the road would take all of my concentration, never mind trying to learn your signal system.