A civil engineer, which I am not, could explain to you that traffic flows in a predictable wave pattern. This reality is what's used to keep other major cities from encountering gridlock.

The answer to the problem was presented to the Metropolitan governor years ago: get rid of all the policemen sitting in booths manually switching their own intersection's lights and put in a city-wide automated system which is calibrated for the ebb-and-flow of Bangkok's traffic. Will that cure everything, of course not, but it would make things flow a lot more smoothly.

So the hurdles to simply implement the solution are two-fold: 1) what to do with the hundreds (thousands?) of obsolete button pushers? and 2) how to replace the revenue streams from all the folks that pay to have their route turn green for them when they call ahead?

This is a hidden fact of Bangkok life: people pay to keep their intersections moving. Ever wonder why a light is 2 minutes one day and 7 minutes the next at the exact same time of day? This wreaks havoc on all the other sois and thanons into feed into that intersection and the waves of traffic that begin spiralling outward behind them...