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Why does the signal include an amber and green light?
by femto 10y ago
Why does the signal include an amber and green light?
- cperciva 10y agoProbably because including two unused bulbs is cheaper than custom-making a single-bulb traffic light. (Also, people who are used to seeing a set of three bulbs might not recognize a single red light as being a traffic light at all.)
- kuschku 10y agoActually, it’s not that easy. German traffic lights are a modular design, and ones with only two or one bulb are common. (You can stick as many modules together as you wish, or remove them)
- pluma 10y agoThat doesn't sound entirely true. I've only seen one-bulb versions for flashing yellow lights (which are sometimes used on crossings to indicate "pedestrians are crossing" at difficult crossings, typically when more than two roads meet and the pedestrians could easily be overlooked). I've only seen two-light versions for pedestrians (i.e. red and green). I think I've seen other one and two bulb versions on non-public roads (e.g. industrial sites) but that's about it. I've never seen a version with four bulbs. And you make them sound more modular than they are: while the part containing the bulb seems to be generally modular the case containing these modules is generally fixed for a certain size. So adding or removing modules after they are deployed is not as straightforward (except maybe for temporary traffic lights). I've actually seen the auditory clue box (whatever it's called -- the ticking thing at crossings to help blind pedestrians cross safely) replace one of the bulbs (on three-bulb lights where there is a redundant second red bulb) instead of being added below the traffic light.
- kuschku 10y agoActually, I’ve got a few intersections right near me with such examples. There’s a traffic light for the lane straight forward. Directly next to it is one for those turning right. The forward light has Red, Yellow and Green, the turn lane’s light has only Yellow and Green (both with the arrow overlay). At another one, there’s lights for busses added below or at the side of the existing light, adding one, or two modules (below or at the side).
- pluma 10y agoWhere in Germany are you? I forgot about turn lanes (they often omit the red light when the red phase would be shared with the regular traffic light) but I've never seen bus lights. Might be a regional thing.
- deleted 10y ago[deleted]
- labster 10y agoIn California, I've seen single-socket traffic lights in all three colors. So it wouldn't have to be custom-made. The green ones usually have a directional arrow forward (amber and red usually blink) so they could probably accomplish the same effect with stock parts: red arrow pointing right in a single socket.
- iopq 10y agoJust don't put in new bulbs, then
- ISL 10y agoProbably because it's a traffic light. If it's a traffic light, it'll have to conform to specifications for a fully operational traffic light. Woe unto the traffic-light maintainer if, should the powers that be change the light timing, the light doesn't function correctly.
- whoopdedo 10y agoA color-blind person wouldn't know if a single light is red or green. If the other lamps have bulbs in them, then I'll ask why. But the shape of the signal has to be consistent even when redundant.
- pcmonk 10y agoThis is correct, but I'm not sure the authorities take that into consideration. In my case, it's the yellow and red that look identical, but that doesn't stop them from making single flashing red lights and single flashing yellow lights. Makes life exciting sometimes.
- Buge 10y agoI don't think I've ever seen a single flashing red light that wasn't accompanied by a stop sign.
- simcop2387 10y agoI've seen several in the american south east. Usually around schools or churches (where they'll flash red when church is letting out)
- jsmthrowaway 10y agoIt's not just color blind folks. San Jose's street lights are, to my eyes, damn near the same color as yellow traffic signals. I have to look for lights moving in the same plane as the road unless they're red or green.
- kolinko 10y agoWhat's the difference between flashing yellow and flashing red?
- goodcanadian 10y agoFlashing yellow simply means caution. It is meant to draw your attention, but it has no specific legal meaning beyond that. Flashing red is equivalent to a stop sign: i.e. you must come to a complete stop, but then you may proceed if and when it is safe to do so. EDIT: And for fun, in British Columbia, a flashing green is the same as a solid green except that it usually indicates a pedestrian operated light. I.e. it will always be green unless a pedestrian who wishes to cross pushes a button to activate it. If it is at an intersection, perpendicular traffic generally just gets a stop sign. Moreover, I recently learned that, in Ontario, a flashing green can be used to indicate an advance green. I.e. oncoming traffic is still red, so feel free to turn left.
- tedmiston 10y agoMaybe they change all three bulbs at the same time for uniformity — I don't think I've ever seen a traffic light where one color is burnt out.