How do online mapping tools calculate best distance + time?
How do online mapping sites (e.g.: Google Maps, Mapquest, Bing, AAA) calculate best time for routes, and how do their algorithms differ?
I ask because I’ve had slight-to-very different routings (and different time estimates for the same routings) for different sites, and heck, I’m curious.
This question is in the General Section. Responses must be helpful and on-topic.