The paper investigates the potential for Level 2 autonomous vehicle (AV) technology to improve four prevailing sustainability issues specifically on highways: high congestion levels, increasing accident rates, high CO_2 emissions and poor journey time reliability. 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, CO_2 emissions and journey times can be reduced as a result. The risks of platooning are discussed and a minimum safe platoon headway is established to mitigate the risk of vehicle platoon collisions. This headway is applied to a real highway case study demonstrating the potential to increase notional highway design capacity from 3,600 vehicles per hour (vph) to 9,213 vph, with significant sustainability improvements possible. 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.