Ben Hardy

How can the sustainability of road transport be improved through the introduction of autonomous vehicle technology?

The study investigated the potential for autonomous vehicle (AV) technology to improve four prevailing sustainability issues specifically on highways: high congestion levels, increasing accident rates, high CO2 emissions and poor journey time reliability.

Congestion forms when traffic density increases as vehicles interact to hinder each other’s  progress. To avoid congestion, traffic must maintain similar constant velocities and uniform headways. Co-operative Adaptive Cruise Control (CACC) shows potential to achieve high volume co-operative driving on highways by controlling these parameters and forming vehicle platoons. Accident rates, CO2 emissions and journey times can be reduced as a result.

The practical application risks of platooning were identified and evaluated using kinematic equations. The results indicated that current practical testing schemes are not paying sufficient attention to application risks which increase the likelihood of rear end collisions. A minimum safe platoon headway of 24m was calculated to mitigate the risk of vehicle platoon collisions. The headway was applied to a real highway case study with preliminary findings demonstrating potential to increase notional highway design capacity from 3,600 vehicles per hour (vph) to 7,770vph, suggesting that significant sustainability improvements are possible.

A back-casting exercise was conducted identifying that achieving high volume deployment of CACC on highways will necessitate the implementation of various national transport policies and further development of CACC; tasks that could take at least 20 years to complete. It was also discovered that forecasted increases in global road transport demand could generate traffic volumes that may overwhelm highways even where AV technology is present to increase maximum traffic throughput.

Recommendations are made to complete a number of policy implementation and technology development tasks aimed to create the best chance of achieving the identified sustainability benefits within a 20 year timeframe.