How self-driving cars will think ahead to keep you safe
9:00 AM | September 29 2016

How self-driving cars will think ahead to keep you safe

Mattias Brännström, senior researcher at Volvo Cars, explains how self-driving Volvos will be ‘taught’ to think ahead to make sure you arrive at your destination safely.

How do you ensure that autonomous cars drive safely?

“The key is in spotting a potential danger and ensuring that we don’t end up in a situation where an accident becomes unavoidable. At Volvo Cars, we are very good at active safety: collision avoidance and warning. But the current systems are reactive – they don’t plan ahead. Their job is to save a driver who ends up in trouble, and they will do their best to save the day.

“With autonomous driving, we have to think differently. The safety systems have to become proactive, not just reactive. Our autonomous vehicles will not only act on what they can see, but also on potential dangers which have not yet been observed.”

What does that mean in practice?

“If we approach another vehicle that is parked next to the road, we need to make sure that we don’t drive too fast or too aggressively. Someone might open the door or a pedestrian might walk out from behind it. We know the capability of our own vehicles, so we can calculate the margins we need to avoid a collision if the situation changes suddenly. That means we don’t put ourselves in a situation that may seem harmless, but could actually lead us into a dangerous situation. At the same time, we don’t want to be over-cautious. The challenge is to enable driving with a margin that’s both small and at the same time safe.”

So, what is a ‘safe margin’?

“It means giving ourselves enough time and space to react if something unexpected happens – to allow our systems to kick in and prevent a collision. We constantly calculate margins for a huge range of potential hazards and are ready to apply a backup solution when necessary. So, we could slow down, steer or even speed up, depending on the situation. Since we know the capabilities of the car, we know exactly what this margin has to be. “Our ambition is to drive safer than a human driver”, says Mattias Brännström. “Imagine you are driving past a school. As a responsible driver, you’ll slow down because you know that suddenly there might be a child appearing out of nowhere. You allow yourself time and space to brake if that happens – that is your safety margin. We do exactly that.”

How does it work?

“We have algorithms that are fed lots of data from the sensors in our car. We know where we are, where we’re going and where other road users are. Then we calculate a whole range of possible trajectories for all other road users. They might behave as you’d expect, or they may not – another road user might make a mistake or suddenly appear. In other words, we account for the uncertainty of future events and the capability of the sensors. When manoeuvring, we need to be aware that things might change suddenly. And we also need to be aware that a human driver will have a longer reaction time than a self-driving Volvo.”

Are you teaching Volvos of the future to drive defensively?

“Yes, this is what we call precautionary safety at Volvo Cars. Driving safely is not such a great challenge if there are no obstacles or other road users present. But to drive safely in dense traffic is much more difficult. The great thing here at Volvo is that, thanks to our active safety systems, we already have so much knowledge on how to avoid critical scenarios. And we can build on this knowledge when developing technology to drive with precaution.”

How do you enable safe driving in dense traffic?

“The principle is quite simple. We create a margin of safety for Autopilot functions such as the automatic lane change. There has to be enough space and a margin of safety for Autopilot to perform its manouevre. If there’s no margin, there’s no lane change. We won’t give permission.”

So the safety aspect of Autopilot is in charge?

“In a way, yes. It’s like a driving instructor. We calculate margins, we give advice and we intervene. If the car doesn’t behave properly, we can kick in and avoid a risky situation. And all this goes on without the person in the car noticing. We are aiming for a smooth and confident experience – just like a good chauffeur.”