Approximately one third of car trips involve one or more passengers and yet we know little about how the presence of a passenger helps or hinders safety and efficiency. To date, research in this area has focused on the possible distractive effects of passengers. Although we know that drivers conversing on a mobile phone is distracting and unsafe, epidemiological studies suggest that driving with a passenger has a lower crash risk than driving alone. This paper describes two studies into how drivers and passengers interact during a journey; a survey regarding the most common actions of passengers and how drivers view their helpfulness, and an on-road study of driver and passenger interactions. The results indicated several areas that drivers felt passenger assistance was quite helpful, but in some cases was exhibited very rarely. The on-road study revealed some interesting gender differences in who offers driving support, and who requests it. By understanding how passengers can contribute to safer journeys we can provide that information to drivers at risk, such as those very early or late in their driving careers.