For economic and social reasons, enhancing traffic efficiency is vital. This research investigates improvement in efficiency based on driver behaviour on a generic three-lane highway in Ontario. These behaviours include law-abiding Normal drivers, opportunist Deviant drivers, cautious Non-Myopic drivers, tailgating Aggressive drivers, and ambivalent Imitator drivers. Generally, overall traffic efficiency declines with higher car densities. However, efficiency does improve with the presence of Deviant and Aggressive drivers, and Non-Myopic drivers do not affect traffic flow. Imitators are Normal drivers who temporarily mimic deviating driver behaviour. Imitator drivers fare worse than Normal drivers, but slightly improve overall system efficiency.