Autonomous vehicles continuously make choices that affect other road users. These choices can cause inconvenience to third parties. The irritation this can cause human drivers can lead to irrational driving behaviour, which can create dangerous situations. Teaching autonomous vehicles courteous driving behaviour can minimise the discomfort the vehicles cause to other road users, which can increase road safety.
This is according to research by Liting Sun, Wei Zhan and Masayoshi Tomizukade from the Department of Mechanical Engineering and Anca Dragan from the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. All kinds of techniques have now been developed to allow autonomous vehicles to manoeuvre safely through traffic. This involves anticipating the behaviour of human drivers so that the autonomous vehicle can make efficient movements without colliding with other vehicles.
Selfish driving style
The trade-offs that autonomous vehicles make are generally aimed at striking a balance between optimal safety, efficiency and driving quality. This can lead to two types of driving behaviour: conservative driving behaviour where autonomous vehicles try to avoid human drivers at all times, and more aggressive driving behaviour where self-driving cars give more weight to their own interests. For example, vehicles that exhibit more aggressive driving behaviour drive slowly forward at an intersection in an attempt to cross the intersection earlier or choose to cut off a human drivers since they have the right of way.
However, researchers point out that the latter driving style can have a negative impact on the driving behaviour of human drivers. For instance, human drivers may become irritated by an aggressive driving style of self-driving vehicles and consequently exhibit irrational driving behaviour, which can create dangerous situations. In a research paper, the researchers therefore advocate a new approach for self-driving vehicles to minimise the annoyance they cause to third parties, teaching the vehicles to drive 'courteously'.
Impact on other drivers
In such courteous driving, autonomous vehicles consider not only the impact of a given choice on their own safety, efficiency and ride quality, but also the impact on other drivers. For example, does an autonomous vehicle's choice cause a human driver to wait longer or be cut off? Such a driving style may also cause an autonomous vehicle to decide to block another autonomous vehicle to increase the safety of a human driver, according to the researchers.
This courtesy also plays an important role in human driving behaviour. For example, people who find themselves in a slow-moving queue of vehicles may decide to stop for a moment to allow another motorist to cross the queue to improve traffic flow, or in tight locations they may allow another vehicle to go ahead despite having the right of way themselves.
Inconvenience of third parties taken into account
"We introduced courteous planning based on the fact that people irrationally care more about additional inconvenience caused by others. Courtesy planning allows an autonomous vehicle to factor such inconvenience into the evaluation of possible plans. We see not only that this leads to more courteous behaviour by robots, but also that this method helps explain data on the driving behaviour of human drivers. After all, humans too tend to behave courteously," the researchers say in the paper.
Researchers' experiments show that a courteous driving style of autonomous vehicles leads to safer choices in some cases. For example, a courteous driving style appears to result in self-driving vehicles keeping more distance from other vehicles while zipping and less likely to choose the same course as human drivers.
Challenges
The researchers point out that courteous driving requires continuous balancing of both the interests of the autonomous vehicle and its occupants and the interests of other motorists. Where the tipping point lies in this trade-off, however, is difficult to pin down.
The researchers also acknowledge that due to the high volume of traffic on roads, it is virtually impossible to always be courteous to all fellow road users, and that some third parties will therefore experience discomfort from autonomous vehicles' choices despite a courteous driving style. The researchers therefore argue that courteous driving helps minimise the inconvenience caused by autonomous vehicles, but cannot entirely prevent inconvenience.
Author: Wouter Hoeffnagel
Source: University of California, Berkeley
Source: 'Courteous Autonomous Cars' paper
Source photo: Pixabay / Free-Photos
