A data question really, though there may be a useful geo-processing solution.
Context: I am calculating "drivetime" catchment areas using PgRouting and OSM / OSM2PO. If my employer/client is to use this as information for decisions, then I think the base data needs to be good.
Problem: The fact is that in a large city say, London speed limits exceed traffic speeds due to congestion. Therefore, my polygons are not really valid (except at times of low activity).
Question: Thus, I'd greatly value any help (all ideas good) with how to update my OSM speeds on an area by area or road by road basis. (E.g: Is there crowd-sourced data (from mobiles)? Can I get access to traffic flow data? Has somebody else tackled this?).
Many thanks, John