Beware of speed limits in SatNav systems

If you rely on the speed limit displayed by your SatNav system or mobile phone mapping app, be aware that they may not always show the correct limit.

A range of data sources are used by these devices to determine speed limits, but none of them are perfect.

SatNav devices like the Garmin DriveSmart series rely on speed limit data published by government agencies such as Main Roads WA. However, both government speed limit data and SatNav map data are only updated periodically rather than in real-time.

Google Maps uses Artificial Intelligence to identify speed limit signs in imagery from sources such as Street View. Since not all road imagery is up-to-date, Google Maps monitors for potential speed limit changes by reviewing app user feedback and analysing traffic trends, but it can take time to identify discrepancies.

Neither SatNav nor Google Maps data reflect short-term speed limit changes such as road work zones and variable Smart Freeway speed limits.

Many newer cars have built-in cameras and sensors that can read speed limit signs on the roadside, including short term changes, but this technology is only effective on roads where speed limit signs are present and clearly visible.

Modern technology in your vehicle, SatNav system, and mobile phone makes it easier to track the speed limit. But remember that this information isn’t always reliable, and drivers remain legally responsible for abiding by the speed limits physically displayed on the roadside.