Plutarch wrote:Can anyone tell me if the pedestrian buttons at traffic lights actually do anything? When I press the button does it make the traffic lights go red any quicker, stopping the traffic and allowing me to cross the road? And - I'm in Britain - are these pedestrian buttons similarly effective or ineffective everywhere?
Signals can operate in several general ways: timed, semi-actuated, or fully actuated.
Timed signals simply run from one phase to the next in a fixed sequence controlled by a simple timer. Depending on circumstances, they can produce much longer delays. OTOH, you cannot run something like the "green wave" of signals (where if you drive the speed limit through one green light, all the lights you hit will be green) unless you have fixed times.
Actuated signals use an induction loop in the road to control when phases change. Semi-actuated signals are when one major street will have a green until a vehicle pulls up over the actuator on a side street. This leaves traffic free to go on the main drag, but allows side streets to turn or cross with a light. Fully actuated signals have induction loops controlling from both directions.
What does this have to do with your question? At actuated intersections, people won't trip the induction loop. If no car arrives going in the same direction you want to walk, you'll wait at that corner all damn day. Pushing the button generates a demand to the signal controller. As people have mentioned, sometimes intersections won't have a phase long enough for a pedestrian to cross, and won't display the "Walk" signal until you press the button because it won't bother making the phase you can cross long enough if there's no pedestrian waiting, because it increases intersection delay. Intersection delay translates to wasted gas.
Fire Brns wrote:I remember reading forever ago on my old computer that removing traffic lights made intersections safer. I'll try and find source. Something about people not liking being herded like sheep.
Traffic signals often increase the accident rate at intersections. However, they change the types
of accidents. Rear-end collisions increase dramatically when lights are installed, but you reduce T-bones from turning or crossing traffic, which are much more dangerous. Depending on the traffic volume, it may not make sense to signalize an intersection. You have to balance the risks of rear-end and T-bone collisions and make a decision.
cream wobbly wrote:Many signs are verbose here instead of there being a Federal standard. Personally, I think the signwriting companies here are the same lot who print football shirts -- must get paid by the letter.
There is a federal standard--the Manual on Uniform Traffic Control Devices, found here: http://mutcd.fhwa.dot.gov/
There is a provision for states to extend from it a bit, but they're trying to rein everybody in. The problem is that we had very widely-separated zones of traffic for many years, and their own traditions grew up in each. It's both expensive for the state and frustrating for drivers to change, especially if the differences are essentially arbitrary. It's easier to have everybody on one standard, but when there's no clear reason to prefer one over the rest, other than "that's how we did it where I grew up, dammit," it can get contentious. California used to number exits sequentially, while the east coast used mile markers. When there were few drivers crossing the country, it didn't matter so much. Now, however...
Also, there's been a push to reduce written signs for many years. However, it's difficult to draft pictorial signs with obvious meaning (Seriously, what does the biohazard or radiation symbols have to do with their respective subjects? You just have to know what they mean.) If you introduce an arbitrary symbol, you then have to get everybody to learn what it means, and it's not politically possible to make all drivers read new rules and take a test every year.
My traffic professor had us do an assignment once: Create a sign to warn drivers of Canada geese crossing the road. A week or so later, we had a vast variety of permutations turned in and posted up in the front of the class. He went to the first one, and asked "How can I tell that this is a Canada
goose?" (It didn't have the characteristic white band around the throat.) He went to the next one, with a well-drawn silouhette of a Canada goose standing, white throat and all. He asked, "Does this mean that driver's have to watch for just standing geese? What about crossing geese?" The one with a flying Canada goose silhouette, he asked if about ones standing or walking across the road. The sign saying "Canada goose x-ing" he picked at whether people would understand the "x-ing=crossing". And for the sign "Canada goose crossing"--"What if they can't read?"
Seriously, sign design is fucking hard