I'm talking about speeds that can be consistently measured, whether
because of consistent rush hour conditions or other factors.
I wouldn't use 'average speed' for the tag, because it implies
something else, but that's what the OP chose for this thread. 'traffic
speed' or something like that would be better.
I'm not talking about "the fastest speed you can drive down this
curving country road", which I agree is going to vary depending on the
driver etc.
If I go to the nearest main road to my house in between the hours of
16:00 and 18:00 every weekday, I can measure the speed at which the
traffic is moving. It will be consistent every day. It will be
significantly lower than the 'maxspeed' (something like 1/5th
maxspeed, like 8mph). All of the motor traffic will be travelling at
this speed (it's so slow that 'slow' drivers will not be left
behind!). For the rest of the weekday daytime the speed is more
variable but is also significantly slower than the maxspeed. Only late
at night/early morning is it physically possible for the traffic to
get up to the maxspeed.
In UK cities, I expect many roads are like this. As you may imagine,
using the raw maxspeed for routing (as all the routing systems and
online routers I have ever used seem to do) is useless in this
situation. Not only is the 'time to destination' totally incorrect,
the route chosen is often wrong as well, because choosing a slightly
different route would make journey times much quicker.
Routing programs can't use heuristics to work out these speeds, they
are too dependent on local micro-conditions. But we can measure them.
Woll
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