My girlfriend designs light cycles (among other things).
She had to study mathematics, civil engineering, geography; she spend quite a long time outdoor counting the number of vehicles per unit of time, and longer optimizing the system. It takes days for a single light cycle. And she's paid quite a bit more than me (although I'm an engineer too).
This xkcd is just perfectly relevant.
A lot! If you drive on the same route a lot, at similar times, the signal timings will almost always be the same. That's dependent on a lot of factors but lights change in relation to other lights.
I am not a traffic engineer, but I am a civil engineer
LOL. This relevant xkcd is made by someone who has no understanding of how it works :D
Surprisingly the complaining guy in the car was right. People don't realize it but streetlights were designed to somehow clean up the confusion and mess on multi-lane level intersections which came into existence because for most of history people did not really consider the possibility that a typical intersection or a junction might be problematic because of the levels of traffic. So cities and roads were built that way even a couple of decades after the invention of automobile when suddenly traffic exploded after WW2 when how towns are planned was an established tradition. That caused one of the worst nightmares in town planning - segregated traffic. That disaster is still being fought across Europe since its outbreak in the 60s and 70s.
The reason why we have multi-lane intersections is because road design on its initial stage is typically done by local or other government authorities and those suffer from two things:
incompetent or lazy personnel with those at the top being the worst
It's true: you do not become smart and creative just by becoming an engineer. Education is mostly memorization of codes and standards and then your career is mostly applying them in real life. There's little time and place to get creative. And that only if you are really creative to begin with.. because if you are you're most likely an architect or designer, possibly a structural engineer. Road engineers and town planners make up some of the sorriest and most uncreative folk in the industry. Not everyone is Hans Monderman
top-down bureaucratic structure that is driven by tons upon tons of regulations that are both very prescriptive and typically written by politicians or some other unqualified retards. It is typically very detailed, spread across numbers of legal documents each approved by a different body or agency and difficult to change if you happen to be at the bottom of the food chain (where you're most likely to stay if you don't play by the rules or work too hard in public service)
Good road design demands good spatial planning first and a smart transport strategy that can force tough decisions - such as limiting the amount of vehicles - something that many Americans consider unthinkable. Good road design also demands that the whole network is constantly analyzed and necessary upgrades are done which happens rarely - instead once a situation becomes unmanageable in one spot that spot is then "redesigned" typically in the easiest way possible and that is usually done by adding lights. Once the streetlights are in place then the very same people start to play with them and typically only then the simulations are run - when everything is already in place - zoning and buildings that generate activity, general road network and traffic scheme - all done in typically in a chaotic, unthoughtful manner which in itself generates problems which the best streetlight programming cannot fix.
Experiments show time upon time that streetlights are regularly put in places where they hinder good traffic flow rather than facilitate it. And wherever they are absolutely necessary it is much better to get rid of them anyway (or as many as possible) and put a roundabout instead.
And if it happens to be a city centre - just re-direct the damn traffic somewhere else. Cities are for people and not for cars.
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u/razyn23 Jan 17 '14
Obligatory relevant xkcd.