Special Sub-Topic: Have You Got a Light, Boy?
|Let's start with a simple signal which, while not used in every jurisdiction, has the same meaning everywhere it is used: a flashing red light. Which traffic sign is this light equivalent to?|
Stop. Most North American drivers will of course recognize this particular, common signal. However, according to the Vienna Convention on Road Signs and Signals (which neither the USA nor Canada are part of), designed to unify traffic signal meaning across the world, this usage is not permitted; flashing red lights are only to be used in pairs to indicate a stop in front of a particularly severe danger (raised drawbridge, railroad crossing, etc.). It should thus be expected that the use of the red flashing light at intersections will decline over the years (the Vienna-compatible way to enhance the visibility of a "Stop" aspect is a normal Stop sign combined with a flashing amber signal).
|Here's a mostly European one: Before going from red to green, some European countries display red and amber simultaneously for one to two seconds. Which common feature of European cars is this aspect catering to?|
Manual gearboxes. Unlike automatic transmissions, manual transmissions require a certain amount of time to get ready for departure - depress clutch pedal, choose first gear, possibly release hand brake and then slowly release the clutch to depart. To give drivers the opportunity to do so in the last seconds of their imposed wait and to be ready when the light turns green, the red-amber signal is used. It is in all other aspects to be treated like a red signal and penalties for early departing can be assessed up to the same amounts as those for running a normal red light.
|Red, amber, green and... blue? Indeed, some cities in Germany added a blue aspect to their traffic lights in the 1980s. The blue light also showed a white key, but what did it mean?|
Long red - turn off engine. The "engine off" blue was one of the early attempts at helping drivers conserve fuel. It was typically used at intersections where the red duration was 60 seconds or more. The light was solidly lit for most of the red, asking the driver to turn off the engine. It went off about 20 seconds before green (keep engine off, but do not turn off if just arriving) and then, 5-7 seconds before green, came on flashing (restart engine).
While a good idea in principle, the light had several flaws. First, too few drivers heeded it, second, of those who did heed it, few restarted the engine at the correct time (either immediately upon going off, massively reducing the benefit or only when the red-amber came on, leading to delays) and finally, it broke the important rule that the only permitted usage of blue in a traffic-relevant lighting fixture is that of the blue emergency vehicle light.
|Staying in Germany's history for a moment: In East Germany, traffic lights not only showed the red, red-amber, amber and green aspects but were capable of a fifth one, meaning the same as a flashing green in some other countries. What additional light combination did they use?|
Solid green and amber at the same time. The green-amber combination was an early warning that a light would turn red and preceded the normal amber. Under East German law, you were supposed to drive slowly enough that you would be able to initiate a stop before the light turned amber-only and entering an intersection under a solid amber would already cause you to get fined (albeit not as harshly as on a red). Green-amber is also used in some Scandinavian countries and in Italy. In both cases, it replaces the normal amber between green and red. The other, rather confusing, combinations, are thankfully all my own invention.
|In European countries, most pedestrian lights use pictograms of a red standing man and a green walking one. Germany has a particularly wide selection of these: The original West German one, a new stick figure, the nostalgic East German "Ampelmännchen" and a fourth, officially not permitted but increasingly common version depicting what?|
A girl with braids. The German road code currently prefers the stick figure icon for pedestrian lights. The old West German "man with hat", a relatively badly recognizable design, is considered legacy (it is no longer recommended to be installed, but remains valid and has no "replace by" date). The much clearer, iconic East German variant was originally considered deprecated and should technically be gone from the streets by now, but cities and citizens were resisting the move, even installing new East German style lights in West Germany. As a result, it is now allowed again in legacy status. The girl is a spin-off design made to resemble this man in style, but clearly female; many cities have a small number of her (often only one or two), usually at high profile locations with lots of pedestrian traffic such as a pedestrian zone crossing a major road to maximize the impact.
|Off to Canada! Some Canadian intersections have the overhead lights mounted horizontally instead of vertically. Since this takes away positional information important for color-blind people, these lights often employ shapes to convey their aspect to them. Which is the correct assignment of shapes to colors?|
Red: square, amber: diamond, green: circle. Technically, a horizontally mounted traffic light does not need a shape encoding of its colors any more than a vertical one since the order of lights is fixed (red always needs to be closest to the median and oncoming traffic). Yet, the possibility for confusion is higher than with a vertical light (a driver from a country that drives on the left would possibly misinterpret the Canadian light), so the shapes add extra safety. Switzerland also occasionally uses shape-enhanced horizontal traffic lights; they also use a square for red, but a circle for amber and a triangle or arrow pointing in the direction open (left, right or straight) .
|Not every vehicle needs to heed the normal lights. In particular, trams and buses often have their own set of lights, usually composed of white and/or orange shapes. While these lights differ in detail from one city to the next, some signals are universal, especially the white bars. Which of these four bars conveys a very different meaning than the other three?|
The horizontal bar. While sharing the road with normal cars, buses and trams often have a separate signal set that allows them special privileges like early departure so they can make a turn before the other traffic can block them. This is done to optimize the flow of both public and private transportation on limited space. The main "stop and go" signals for them are usually derived from train semaphores - a horizontal bar means stop, a vertical bar means go (straight) and a slanted bar allows for a turn in the direction of the slant.
|An amber flashing light always has a "caution" meaning. Which of the following meanings for "flashing amber" is NOT an actual meaning used in at least one European country?|
Proceed; speed limit of 30 kph until next light. Flashing amber is universally used as a signal of caution without conveying a hard "stop". It is used in many central European countries if a traffic light is inoperable (due to a malfunction or intentionally), France uses it instead of green to indicate that traffic may proceed but turning traffic has to yield to conflicting traffic and in the UK finally, the flashing amber is used at certain pedestrian crossings - the lights first go red for only a few seconds to stop traffic and then change to flashing amber, indicating that drivers may start as soon as the roadway is clear, thus minimizing delays.
Using the flashing amber for speed limit indications is common in train signals, however, it is not part of any road code in the world.
|In some places, notably in Switzerland, you will find intersections where the default setting of traffic lights is to have all directions show red lights, both for vehicular and pedestrian traffic. Which type of intersection would be most suitable for such a setting?|
A rural intersection with low to moderate traffic. An all-red setting is used in conjunction with detection loops for approaching cars at low-traffic intersections to minimize the probability that a car might have to stop. The default state of all red minimizes the time required to give any arbitrary direction the green light (the signal does not have to wait through an amber phase), so usually by the time a driver would start braking for the red, they will already have the green light and can pass immediately. In an ideal case, cars will have to stop or slow down only if there truly is conflicting traffic.
|Finally - like every item of technology, traffic lights can malfunction, with possibly disastrous consequences. Which of these malfunctions does not need special circuitry to detect it and, if found, immediately switch the lights into a safe failure mode (e.g. 4-way flashing red or off)?|
Failure of an amber lamp. There are two very dangerous situations possible with a failed traffic light: The first is the failure of a red aspect, which, even with the rule than a dark signal is equivalent to a stop sign, may have disastrous consequences in low visibility where the driver might not even know about the signal being present. Even more dangerous is the state of conflicting greens - two streams of traffic with a potential to collide are both given a right of way indicator which drivers have of course learned to rely on. Crashes resulting from conflicting greens are also usually very dangerous since they usually happen at high speeds and awkward angles where the passive safety of the cars involved is rarely operating at its best. As such, they need to be avoided at all cost - in the European Union, a traffic light is required to have independent circuitry to react to a conflicting green and switch off the light in 0.3 seconds, regardless of any other circumstances.
A failed amber lamp, however, is not hardly as dangerous - the short duration it is lit means that drivers needing to react to it will have seen the green before it would have come on or will see the ensuing red in time to stop. Also conflicting traffic is still stationary and will be able to react in time to prevent a collision with a car coming through in the first one or two seconds of red. It is still something that should be repaired quickly, of course!
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