We definitely need an "average speed" tag, to improve routing.
In my area the road speeds vary a lot depending on the amount of
traffic, which means that the "fastest" routes selected by routing
algorithms are often not good because the journey goes along roads
where the traffic is nearly stationary, whereas slightly different
routes would be along 'empty' roads! The tagged or implicit
'max_speed' is useless as a routing speed for most of the day on these
roads.
We would need to:
1) Tag the 'average' or 'typical speed'
2) Associate those speeds with time of the day/week.
3) Allow specification of different speeds/time for both directions of
a way (rush hour traffic is often only in one direction).
4) Allow the mode of transport to be specified (e.g if there are bus
lanes, then buses would have a different speed to car stuck in rush
hour traffic).
I've done some very cursory searching on the wiki, but not found any
suggestions/proposals for this yet.
"rush hour" traffic speeds are much more regular and consistent than
"the fastest speed you can drive down this curving country road", so
maybe the latter is a separate tag/discussion.
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