Why quality of digital maps matters for Intelligent Speed Assistance (ISA) compliance

From July 2022, all new vehicles brought to market in the EU must be equipped with an Intelligent Speed Assistance (ISA) system, which requires speed limit data from both cameras and digital maps to pass vehicle type approval. Here’s how TomTom is helping OEMs accelerate ISA compliance with road-tested ADAS Map Speed Limits.

The European Union General Safety Regulation (GSR) requires all new cars, vans, trucks and buses to be equipped with a range of new vehicle safety features from mid-2022 onwards. The measures represent a big step forward for road safety, and are predicted to prevent as many as 25,000 road deaths over 15 years.

Key among these new technologies is Intelligent Speed Assistance (ISA), an overridable safety feature that informs drivers of the current speed limit and, when needed, acts as a speed limiter – automatically reducing a vehicle’s speed by limiting engine power.

All road users stand to benefit from ISA, which is estimated to reduce road accidents by 30% and deaths by 20%. For vehicle makers, however, there are several challenges to be overcome – within a very short timeline – to ensure full compliance with the new legislation.

Rising to the challenge

The requirements are clear (and extensive): The ISA system must be able to perform at a high level in many different driving scenarios and provide balanced performance on all kinds of roadways, including highways, city streets and rural roads. The system therefore requires digital map data fused with a camera, and a processor that can merge all this data to provide drivers with constantly updated speed limit alerts. This needs to be built into all new vehicles to pass type approval – even in models without embedded navigation.

Finally, ISA performance test involves completing a 300-400km (186-248 mile) test drive and demonstrating that the ISA system provides over 90% distance-based correctness over total distance. In addition, the system must have a balanced performance with at least 80% of the distance driven on each of the three road types (urban roads and streets, non-urban roads, and motorways). This is valid for explicit speed limits signs, with a numerical value, and implicit speed limit signs, without a numerical value such as a highway entry sign.

It’s a tall order for OEMs to meet. How can they create an ISA system that complies with all these requirements—in time for July 2022 at reasonable costs? It all starts with having the right map data and supporting horizon software.

Beyond camera-based speed limits

As mentioned above, camera-based systems alone aren’t enough to pass ISA regulation: Vehicle makers also need a reliable map. That’s because cameras can sometimes misinterpret speed limit signs or have an obstructed view. Camera-based speed limit recognition can thus lead to errors when the camera cannot correctly recognize road signs, and research has shown that cameras perform at about only 50% correctness.

In many countries, different speed limits apply for large vehicles than passenger cars, but these aren’t always shown on regulatory signs – and thus can’t be captured by cameras. Take the Netherlands, for example. Heavy trucks and buses must stay below a general speed limit of 80 km/h (50 m/h) on expressways and motorways, which is lower than the posted speed limit of 100km/h (62m/h).

Likewise, there are many conditional and implicit speed limits that are difficult for cameras to interpret correctly, such as a highway or a city sign without an attached speed limit. European vehicle safety ratings prove time and time that cameras struggle with implicit speed limits such as residential area entry signs.

The advantage of a map-based ISA system is that it offers accurate speed limit information irrespective of road conditions and recognizes implicit speed limits.

Taking ISA further with digital map data

The TomTom ADAS Map provides highly detailed and accurate map content to support vehicle safety features like ISA. By fusing digital map data with information from car cameras and other sensors, in-vehicle systems gain better insight into the road ahead.

TomTom ADAS Map Speed Limits includes attributes that indicate the allowed legal speed limit for a certain road segment and vehicle type, as well as different types of speed limits, such as:

• Implicit speed limits that are present when, for example, entering an administrative area.

• Explicit speed limits, which can be captured from posted speed limit signs.

• Conditional speed limits that can be, for example, vehicle specific, weather dependent, time dependent and others.

To support more sophisticated ADAS use cases, such as predictive powertrain control (PPC), TomTom’s ADAS Map also delivers precise road gradient, curvature and lane information. TomTom has a complete offering for ISA: Besides the TomTom ADAS Map we offer an ADASIS-compliant horizon software.

Putting our maps to the test

Today, more than three million vehicles on the road – both private and commercial – drive with our ADAS map. Vehicle makers all over the world trust TomTom for some of the highest-quality ADAS map speed limits in the industry, built through a transactional production process and proven with continuous benchmarking. We regularly audit our ADAS Map Speed Limits. These audits confirm that our map content meets strict ISA requirements and quality targets.

This year, we performed regular ISA-specific test drives with our ADAS map, covering a balanced range of roads including highways, cities and non-urban areas. Such tests have proven that our combination of ADAS Map Speed Limits and camera data delivers a performance rate of over 90%.

In sum, TomTom ADAS Map quality is already proven to be compliant with ISA legislative requirements, today!

We’re also bringing in more high-quality data all the time, using input from survey vehicles, third-party sources and our network of half a billion connected devices. It means that if speed limits or other road conditions change, it’s reflected in our map – making sure ISA systems always have the most up-to-date information.

Moving towards a safer future

ISA will soon help road safety take an important step forward – and trusted TomTom maps are here to help OEMs meet the change today. With tried and tested ADAS Map Speed Limits, vehicle makers can speed compliance with ISA legislation, ensure a better experience for drivers and make the roads safer for us all.