As driverless technology has edged closer to market, a number of studies have attempted to predict what impact the technology might have on traffic levels.  For instance, a paper published last year by Arthur D Little found that, in the short-term at least, congestion is likely to get worse after the introduction of autonomous vehicles.

This is likely to occur as driverless cars share the roads with human drivers in a combination that the researchers believe will increase traffic jams by around 16%. The results emerged after a micro-simulation was undertaken at a major intersection in Frankfurt that is notorious locally for the scale of traffic jams during the evening rush hour.

A second study, conducted by the UWICORE laboratory, also urges a degree of caution, noting that there are unlikely to be any real traffic improvements until autonomous vehicles make up at least 15% of all vehicles on the road.  That is, at least, unless specific solutions are developed to ensure the efficient coexistence of autonomous and regular vehicles.

Easing congestion

One of the major selling points of autonomous technology is that it will make our roads more efficient, not least by allowing for the creation of platoons on highways.  The fact that vehicles will be able to travel so close to one another promises to make them more efficient and reduce congestion.

The research suggests that such gains can only be realized however if solutions are not present that guarantee that safe and efficient coexistence of conventional and autonomous vehicles.  If such solutions don’t exist, then it will require at least 15% of vehicles to be autonomous before any efficiency gains are seen.

The authors believe that this is largely because the various manoeuvres of autonomous vehicles will have an impact on conventional motorists, and indeed vice versa.  For instance, the act of creating a convoy of autonomous vehicles will probably result in conventional vehicles around them slowing down to allow it to happen.  Indeed, the conventional vehicles might obstruct the convoy from forming in some way.  The researchers believe that as many as 50% of autonomous driving manoeuvres may be obstructed in some way, whether deliberately or otherwise.

The benefits of autonomous technology aren’t likely to materialize, therefore, unless solutions are developed that assist driverless technology in functioning alongside conventional motorists.  Of course, eventually the number of autonomous vehicles will grow and their proportion of overall vehicles with it.  When their number reaches around 50% of all vehicles on the road, the authors suggest that road capacity could increase by up to 40%.

There will come a period of adaptation before then however, and this study provides a valuable prod to encourage us to think now of some of the things that integration might require for it to go smoothly.