Objective: To compare the risk of road traffic injury calculated using an exposure measure based on people's mobility, person-hours travelled (person-hours), with the risk obtained using population census, vehicle fleet and vehicle-kilometres travelled.
Methods: The rate of road traffic injury on a working day in Catalonia in 2006 was calculated using the number of people injured from the Register of Accidents and Victims of the National Traffic Authority and as denominator: person-hours travelled, from the 2006 Daily Mobility Survey of Catalonia; population census and vehicle fleet, from the National Statistics Institute; and vehicle-kilometres, from the Ministry of Public Works.
Results: Compared with person-hours travelled: population census may underestimate the risk in groups with low mobility; vehicle-kilometres may underestimate the risk in regions with high level of non-motorised mobility and high use of public transport; vehicle fleet may underestimate the risk for collective forms of transport such as buses and for motorcyclists who make many trips but of short duration.
Conclusions: Measures of exposure involving people's mobility should be used in the estimation of road traffic injury risk, instead of vehicle's mobility, population census or vehicle fleet.