Consider this a bit of a Saturday morning throwaway post 
This may be a case of “duh”, but since traffic data for England went live on the iPhone’s Google Map, I’ve been badgered to find out exactly what the road colour scheme means. I had a quick look at traffic on a desktop Google Map, and saw:
As far as I can tell, there is no black and red indicator on the iPhone’s map, just red. So we’re left with:
- Green: 45mph+ (Billy Whizz)
- Yellow: 25mph+ (just about cruising)
- Red: 0mph+ (going nowhere fast)
There’s also grey which, according to Paul Stamatiou, indicates no data available. By the way, there’s no traffic data available yet for Scotland, Wales or Northern Ireland…