Research & reports

Title: Driverless vehicles: impacts on traffic flows

Organisation: Department for Transport
Date uploaded: 17th January 2017
Date published/launched: January 2017

This study suggests that driverless cars could significantly reduce delays. The project used computer software to create virtual models of different parts of the UK road network including urban roads and a 20km motorway section. Delays and traffic flow were all shown to improve as the proportion of automated vehicles increased above specific levels.

The study suggests that driverless cars offer major potential benefits when the proportion of them on the road is higher than the proportion of older, more traditional vehicles.

The study examined different scenarios including the level of automation, the proportion of vehicles equipped with the technology and different automated driving styles.

The main findings of the report included:

• On major roads where traditional vehicles outnumbered automated vehicles benefits are relatively small, but increase as the percentage of driverless cars on the roads increases - when measuring peak traffic periods with a maximum of up to 100% of driverless vehicles journey times reduced by more than 11% and delays cut by more than 40%.

• On urban roads benefits are seen in peak traffic periods even with low levels of automated vehicles on roads - benefits include a 12% improvement in delays and a 21% improvement in journey time reliability.

Please note that this report is largely an analysis of the flow performance, and therefore doesn’t cover in detail:

• The safety impacts including the interaction of fully autonomous, semi-autonomous and fully manual vehicles

• How the availability of autonomous vehicles – owned or per-trip e.g. as taxis – will change demand and use and the knock on effect on safety urban and rural roads.

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