Traffic sign recognition (TSR)

Traffic sign recognition (TSR) is an advanced driver-assistance system that recognizes traffic signs and notifies the driver of them. The system is mostly used to detect speed limit signs but modern systems can recognise a variety of other signs also.

How does traffic sign recognition work?

TSR systems use forward-facing cameras to “see” signs. Then it applies image processing techniques to detect which sign it is. The camera is usually mounted in the windshield near the rearview mirror. Early systems detected only speed limit signs using colour- and shape-based technologies. Now, many systems use machine learning that allows them to detect a huge variety of different signs.

Once TSR has recognised the sign, the system displays it to the driver in the dashboard or on the head-up display. In some cases, TSR also works together with the navigation system to provide the driver with the information even when a sign is hidden by, for example, snow or branches.

Most traffic sign recognition systems only display the signs. But some let the driver reach the speed limit with one push of a button when using adaptive cruise control (ACC) or sound an alarm when the speed is above the limit. Some systems even adopt the speed limit automatically when using ACC.

Advantages and disadvantages of TSR

The purpose of traffic sign recognition, like any ADAS, is to lower the possibility of an accident resulting from distractions and sleepiness. But it also makes driving more convenient and automatic. When you happen to miss a sign by the road, you can just see the limit from your dashboard or hear a signal from the car that alerts you to the high speed. This way, you can be sure that your driving speed is within the suggested safe limit.

TSR is also important for the development of self-driving cars. These cars need to be able to understand all traffic signs and act accordingly. This need has brought about great advances in this technology making sign detection faster and more accurate.

On the downside, TSR is limited to roads with clearly visible signs. When the signs are damaged or hidden, it might have trouble recognising them. Extreme weather conditions such as heavy snow, rain, or fog can also make it hard to detect the signs.