the UK, Iceland and Argentina (there may be more) the sequence goes:
R, R+Y*,G,Y*,R. (* a few seconds at most). Legally you can only proceed on green â the R+Y is only a warning.
The yellow phase when going from green to red varies a little in its timing, but in my experience it's generally shorter in the U.K. than on most American signals. Our peculiar R+Y phase seems to be fairly constant -- I'd estimate about 2 secs.
We also have lights which are not at an intersection, but instead are located in the middle of a road to allow pedestrians to cross. The sequence on those is different: G, Y, R, Flashing-Y, G. The flashing-yellow phase is longer than the normal R+Y phase, and corresponds with the time when the pedestrian light is flashing before going back to red.
The pedestrian light signs and sequences are different as well, but I'd better not get into that!
I remember in grade 12 (long time ago!) , with modular logic units (AND, OR, NOT gates, etc) , making an assembly that generated those aspects â is was quite fun.
I remember just such a project from "Radio & Electronics Constructor" magazine in about the mid-1970s. There were similar projects for railroad signals. That was all at the time when TTL and CMOS logic chips were becoming much more mainstream.
There aren't too many traffic lights around this rural area, but I've noticed a few LED types appearing in the city, about 20 miles away. They really grab your attention for the smart way they "snap" from one aspect to another.
LED lights seem quite popular in France for the repeaters -- The small set of lights that they use mounted low down on the pole so that driver at the front of the line can see more easily.
[This message has been edited by pauluk (edited 02-25-2004).]