The Trafficmaster receiver is inbuilt into your C5.

If you push the Trafficmaster button a message will give you the serial number of your installation.

You the call Trafficmaster and pay an annual fee for 'connection'.

Trafficmaster is a nationwide network of traffic movement sensors (roadside, on motorway bridges etc) covering most major UK highways and alerts the driver aurally of your position and heading together with any slow moving or stationary traffic.

It also gives the expected delay times.

Cheers