Martín-Cantera et al. BMC Public Health 2010, 10:136 http://www.biomedcentral.com/1471-2458/10/136 Page 4 of 9 with questions with three options; low, medium and high risk [44] Table 3 Sample size according to the estimated distribution in age and gender groups Justification For The Study The available research in this field has been revised and a consensus that included recommendations to carry out epidemiological studies in different areas provided. Given the current situation, studies that inform us of the situation at a level closest to the patient (primary health care) are essential. As are studies that permit us to set out risk levels based on a description of exposi- tion to drugs, riskful behaviour (alcohol intake and con- sumption of other psychoactive substances) and chronic and acute health conditions, and studies that assess the RTI risk perception of drivers. On the other hand, the prospective group follow-up can give us an idea of the changes that may appear in terms of RTI risk factors, and in terms of traffic colli- sions with/without injuries. Without a doubt, this is use- ful information in the planning of preventative interventions in primary health care. Objectives Main aim: to assess the distribution of the risk factors associated with RTI in a driving population assigned to a group of participating primary health care centres in the city of Barcelona. Secondary objectives: 1. To study the distribution of RTI risk factors relative to medications, illnesses, alcohol intake and/or consumption of psychoactive substances in the driving population in different groups according to age and gender. 2. To outline the correlation between the number of risk factors related to suffering an RTI and the background of registered collisions, having or not having recieved medical attention. 3. To assess the exist- ing relationship between the self perception level of risk of RTI and the presence of chronic health conditions, medication or consumption of psychoactive substances. Methods/Design Study design Cross-sectional and multicentre study. Setting 25 primary health care centres in Barcelona. Study population Drivers aged 16 or above who have been attended and who have a clinical register at the participating primary health care centres. Sample size calculation The calculation was carried out using the population of men and women with a driving license in the Barcelona 16-24 yrs 25-34 yrs 35-64 yrs Above 74 yrs Total Men 214 Women 171 Total 385 212 173 385 228 157 385 317 68 385 971 569 1540 province from the age 16 and over, according to the 2005 census of drivers made available by the General Traffic Department (DGT). For sample calculation pur- poses, four age groups proportional to women and men were created. Accepting an alpha risk of 0.05 with a precision of +/- 0.05 percentage units in a bilateral con- trast for an estimated proportion of 0.5, a random population sample of 385 subjects was determined for each age group. The total sample size is 1540 subjects (Table 3). Recruitment Process The study population will be recruited by consecutive sampling. Each collaborating researcher, after verifying the inclusion criteria, will include 16 subjects, two for every age and gender group of those described in the table above. All subjects of 16 years of age or over that consult any collaborating health professionals (nurses or doctors) for any motive, will be invited to participate. They will be informed by the collaborating researcher (patient information leaflet) and asked to take part in the study and in yearly follow-ups via telephone. In case of acceptance, they will read and sign a consent form. Each centre will recruit patients until reaching the num- ber of participants stipulated, taking into account the necessary distribution by age groups and sex. Figure 1 Flow Chart: Algorithm of the study shows the recruit- ment system and yearly monitoring. Selection criteria Inclusion criteria aged 16 or above; sufficient understanding and knowl- edge of Catalan or Spanish; possession of valid driving or motorbike license; subject’s agreement to participate in the study and in yearly follow ups via telephone through a signed consent form. Exclusion criteria people who do not poses a telephone contact number; those with serious psychiatric problems; those with phy- sical or psychiatric disabilities that impede their partici- pation in the study; those with a terminal illness. All centres of Barcelona province and the metropoli- tan area will be invited to participate, and those who voluntarily accept to participate will be included in the study. To date, at the end of the recruitment period, 25 practices will participate in the study.