The new study, by The George Institute for International Health, was designed to determine the risk of a crash associated with passenger carriage compared with that of using a mobile phone while driving. Both the carrying of passengers, and having a larger number of passengers in the car, are associated with an increased likelihood of a crash, though not to the same extent as mobile phone use. Earlier studies at The George Institute found that a driver's use of a mobile phone was associated with a four-fold increase in the likelihood of crashing.
The study's lead investigator, Dr Suzanne McEvoy, says that "carrying passengers in the car has a number of potentially distracting effects that also occur with mobile phone use while driving. Moreover, carrying passengers may have additional effects on the driver, including peer influence."
"Drivers with passengers were almost 60% more likely to have a motor vehicle crash resulting in hospital attendance, irrespective of their age group. The likelihood of a crash was more than doubled in the presence of two or more passengers," noted Dr McEvoy.
The study did find, however, that the passenger-related risk is considerably lower than that associated with mobile phone use while driving. The George Institute's Professor Mark Stevenson, who also contributed to the study, suggested that "In contrast to mobile phone use, passengers, with some exceptions, are generally aware of the road conditions and can moderate their conversation as needed."
"However, although the risk associated with carrying passengers is lower than that associated with mobile phone use, it is likely to have a higher contribution to accidents because of the higher incidence of drivers taking passengers as opposed to using a mobile phone when driving," Professor Stevenson noted.
While the body of evidence is increasing in relation to the road safety risks associated with mobile phone use and passenger carriage, questions remain about how these factors impact on driving behaviours. That each contribute to driver distraction is irrefutable, however, passenger carriage by young drivers may have additional effects, as recent studies have indicated. These studies suggest that teenage passengers may increase the risk of crash for young drivers by multiple pathways, which include not only driver distraction but also peer influence.
Dr McEvoy also says that, "Further well-designed research is needed to investigate the factors underlying the increased risk for phone use and passenger carriage and the ways in which the risk can be reduced. Research of this kind can provide an excellent basis for examining road safety policy, with the opportunity to reduce both mobile phone-related and passenger-related crashes and injuries".