https://en.wikipedia.org/wiki/Sydney_Coordinated_Adaptive_Tr...
> On long avenues you just stop every 200m because once the light goes green when you arrive at the next intersection the light there goes red. It seems it is synced, but to the opposite it should be doing.
I recall a link a while back (from HN?) that demonstrated that it's basically impossible to sync green traffic lights in both directions. Any attempt at syncing will priotitise one direction over the other. I can't find the source, and it was so long ago that it's very likely that I'm misremembering.
For a bi-directional green wave, intersections have to be spaced at intervals consistent half the cycle time (times the intended travel speed) of the traffic lights. In that case opposing vehicle streams will always meet each other at an intersection, thereby minimising the green time required along the green wave and maximising the green time available for handling crossing and turning traffic.
If an intersection deviates from that mathematically optimal location, it means that there'll be less of an overlap between the green times for the two opposing direction, meaning that there's less green time left over for cross traffic.
And since in real life, intersections are rarely spaced at the mathematically optimal interval, in practice this means that eventually you have to give up and just favour one direction depending on the time of the day. (To some extent you can try to salvage things by varying the assumed speed between intersections in order to keep the travel time from intersection to intersection constant, but there's only a limited usable speed range between too slow and the legal speed limit.)
And if you attempt to have multiple green waves crossing each other, you introduce even more scheduling constraints which might leave no room for a perfect solution.
These days I assume most people/companies/governments source their traffic flow info from Google because it has more 'active' sensors in so far as every car has at least one mobile phone. Telcos could and should also sell this type of data in an anonymous format. Large toll roads track individual vehicles with a combination of wireless billing systems and numberplate ID so they are effectively able to provide a similar solution for those high value roads.
There is no traffic lights priority for public transport. Melbourne's tram avg speed is 10-15 kph. If you power walk you can go faster than the tram. It just sits there waiting on traffic lights more than moving.
There is no synced traffic lights. On long avenues you just stop every 200m because once the light goes green when you arrive at the next intersection the light there goes red. It seems it is synced, but to the opposite it should be doing.