The questionnaire asked about driving habits, risk exposure, collisions over the past 24 months, socio-demographic information, and cell phone use.Questionnaires were supported with data from cell phone companies and accident records held by police.
The common conception is that passengers are able to better regulate conversation based on the perceived level of danger, therefore the risk is negligible.
A 2009 review by the Hawaiian legislature entitled "Cell Phone Use and Motor Vehicle Collisions: A Review of the Studies" contains an analysis of studies on cell phone/motor vehicle accident causality.
A key finding was that: "No studies were found that directly address and resolve the issue of whether a causal relation exists between cellular telephone use while operating a motor vehicle and motor vehicle collisions." found that response time while using both hands-free and hand-held phones was approximately 0.5 standard deviations higher than normal driving (i.e.
Driver distraction, a sub-category of inattention, has been estimated to be a contributing factor in 8% to 13% of all crashes.
Of distraction-related accidents, cell phone use may range from 1.5 to 5% of contributing factors.
Driving while using a hands-free device is not safer than using a handheld phone to conduct calls, as concluded by case-crossover studies, In some cases restrictions are directed only at minors, those who are newly qualified license holders (of any age), or to drivers in school zones.