What do the messages mean?

The international standard enables us to categorise congestion according to precise rules. Once you are familiar with SUNA GPS Traffic Updates, you will find a high degree of consistency. Here are some tips on what to expect with the most common.

On Freeways:

Congestion: We generally broadcast speed messages in steps of 10kmh. We begin broadcasting when speeds drop to around 50% or more of permitted speed. ‘Stationary Traffic’ means crawling below 9kph. Each speed message is an average measure between freeway junctions.

Incidents: We broadcast the type of incident e.g. accident, road works, special event etc, along with the expected length of delay.

On Arterials:

Congestion: Most delay occurs at intersections, so “average” speed takes into account the time stopped at lights, as well as the actual speed while moving. When we detect serious congestion, we issue a message representing this average speed, or where possible we advise the likely delay instead of speed.

Incidents: We broadcast the type of incident e.g. accident, road works, special event etc, along with the expected length of delay. SUNA GPS Traffic Updates is broadcast using the international standard for real-time traffic, ‘RDS-TMC’. We silently encode the SUNA information in a normal FM radio broadcast. Radio listeners hear nothing, but special TMC receivers decode the information and pass it to your navigation system.