Car: MY13 1.8 EX Auto
Join Date: 7th January 2007
Location: West London
Thanked 1,708 Times in 1,431 Posts
Trafficmaster data can be 15 to 30 mins old.
It goes from their beacons to TMC HQ, then sent to the participating radio stations, then transmitted out.
I used to travel the M25 western section daily. The TMC system used to tell me that the tail of the traffic was at junction 15, clockwise, in the evening peak. My Garmin with digital traffic, updated every minute via Inrix, told me that the tail of the traffic was actually junction 12 or 13, some 5 to10 miles nearer.
Garmin digital was always correct and TMC was completely wrong.
This wasn't just a few days but almost daily.