RAC-Trafficmaster & ITS Holdings are the only licenced providers of over the air RDS-TMC data in the UK and unlike mainland EU needs to be paid for.
RAC-Trafficmaster collect their data via the blue sensors on the road side and those over the third lane of the motorway…
ITS holdings collect theirs from floating points such as Eddy Stowbart trucks and National Express buses….
Both supplement their info using manual input although I don’t know if either also buy in data from the Highways agency eg the Green sensors.
Of late I have been using my CD70 because of a hardware problem with my CarPC and this has given me a chance to compare each side by side on a regular route.
The 07-08 disk has been reliable and provided me with up todate information although not always accurate. Eg the road works currently near Preston on the M6 are indicated to be on the other carriage way to where they are in reality. Both systems seem to be about the same though in accuracy and in some cases giving the right warnings at the right time. This I guess is down to the method of collection.
Reception how ever is another matter…… ITS Holdings use the Classic FM channel to piggy back its TMC data…. This has a very good nation wide coverage while the RAC-Trafficmaster stream is on the back of a number of stations owned by the Chrysalis group. The problem here is that while the data may be more accurate coverage is not as great as it could be and while this is not an issue in the South when looking at a map of each station its clear some parts of the contry ( eg the North are not served that well. In fact this is exactly what I found…. The data is more accurate and detailed yet from my set off point to Liverpool I was only able to access a short burst of TMC data as I was passing Preston in the whole journey.
The problem this presents is that you may miss vital messages of incidents that may affect your journey or even worse divert when you don’t have to because they are no longer valid. I have confirmed these findings with others using different systems and I am not alone in this.
From my point of view I will be selling the 08-09 map as I cant make best use of it due to the poor location and the fact I spend most of my time in the North how ever I will be investing in a Q-Busta also from Trafficmaster because their data is defiantly the best going….. only I’ll have to think a little more my self