Navigant Research Blog

Self-Driving Cars and Real-World Roadways

David Alexander — February 16, 2014

On a recent weekend road trip, I took the opportunity to consider the practicality of an autonomous vehicle doing the driving. The 300-mile journey involved single-lane twisty country roads, dual carriageways (in U.S. terms, a four-lane divided highway), and motorways (freeways). The first part of my journey took place on a narrow country road with speed limits that ranged from 30 mph through small villages to 60 mph on the open stretches. On this route, there were very few opportunities for passing, so the driving process was relatively straightforward. A combination of the latest advanced driver assistance systems (ADAS) should be able to cope with such a drive with minimal driver input.

The next part of the journey took place on a dual carriageway, and again the driving process was quite simple, requiring that my vehicle stayed within well-marked lanes, kept to the speed limits, and avoided running into the back of slower vehicles.  All these functions could be handled by adaptive cruise control, lane keeping, and traffic sign recognition.  The one activity that would need a new system is lane changing to move to the inside lane when not overtaking. Blind spot detection would be a partial solution to this, but it would also need some highly sophisticated decision-making software.

Smoothing the Flow

The bulk of the driving took place on the U.K. motorway system, and the satnav in my car proved that it could handle giving directions to navigate the quickest route. Driving on motorways is where the benefits of autonomous vehicles would be more widespread. For some of the journey, traffic moved along briskly at the speed limit, but as vehicle volumes increased, there were periods where all lanes of traffic slowed down. If all the vehicles in the outside lane used adaptive cruise control, the traffic flow would be much smoother, and some traffic jams would be eliminated.

So the three main parts of my journey could have been handled effectively by technology that is available today. Intersections, however, represent more of a challenge. Simple traffic lights at a crossroads are not too difficult, but some roundabouts are a different matter, and will require considerable development of decision-making software. While the mechanics of driving can be replicated today, the role of the driver cannot. There are many considerations involved in driving, such as estimating closing speeds of vehicles in front and behind to decide whether it is appropriate and safe to change lanes. Anticipating what other drivers will do is another useful driving skill. It may be that an artificial intelligence system that can learn from experience will be a key component of the self-driving vehicle of the future.

10 Years Out

Some of the more advanced autonomous driving features that I outlined above will be coming to market in the next few years. As long as they are treated as driver assistance features, I believe they will be very attractive to customers and will contribute to safer and more efficient road travel. Full details about all the systems are described in Navigant Research’s recent report, Autonomous Vehicles. However, the jump to fully autonomous driving that can handle any situation remains at least a decade away. We can forget about catching up with emails or sleep while the car does the driving for many years, but the number of crashes due to driver error will surely be reduced, and soon.

One consideration for governments at present is how to encourage the development and implementation of this advanced driving technology. On one section of the trip, there was an alternative toll road to the standard highway. It appears that the majority of drivers prefer to travel on the free roads even when road work causes lane narrowing and speed limit reductions. It would improve revenue if more people used the toll road, so perhaps an incentive for drivers who use ADAS would make sense. A toll road that offered higher speed limits for vehicles with self-driving capability would both generate demand for the technology and increase road revenue.

I am looking forward to discussing these and other autonomous vehicle issues with industry colleagues at the upcoming Autonomous Driving 2014 conference in Berlin, Germany, February 27-28, 2014. I hope to share Navigant Research’s perspectives on the topic and learn more about other aspects of this rapidly evolving technology. Let me know if you will be there.

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