Extended Abstract Coxon et al. Proceedings of the 2016 Australasian Road Safety Conference 6 – 8 September, Canberra, Australia Behind the wheel: Process evaluation of a safe-transport program for older drivers delivered in a randomised controlled trial Kristy Coxon ab , Kate Hunter ac , Anna Chevalier a , Julie Brown d , Elizabeth Clarke e , Kris Rogers a , Soufiane Boufous f , Rebecca Ivers a , Lisa Keay a a The George Institute for Global Health, Sydney Medical School, University of Sydney; b School of Health and Science, Western Sydney University; c The Poche Centre for Indigenous Health; d Neuroscience Research Australia, School of Medical Science, University of New South Wales; e Sydney Medical School, University of Sydney, Kolling Institute; f Transport and Road Safety (TARS) Research Abstract A process evaluation was conducted to explore relationships between program outcomes, and intervention implementation from a trial evaluating the impact of an individualised safe-transport program, ‘Behind the Wheel’, for older drivers. Relationships were explored using multivariate linear regression and a logic model constructed to explain program inputs, outputs and outcomes. Older drivers who took ownership and planned for retirement from driving were more likely to reduce their driving exposure. A stronger message was delivered to older drivers with lower function and poorer health. Our results suggest ‘Behind the Wheel’ has greatest impact with older, lower functioning drivers through transport planning. Background Evaluation of intervention fidelity and implementation in clinical trials has gained momentum in recent decades (Bellg et al., 2004; Oakley, Strange, Bonell, Allen, & Stephenson, 2006; Saunders, Evans, & Joshi, 2005). The impact of a one-on-one education-based safe-transport program designed to enhance self-regulation of driving among community-living older drivers was recently evaluated in a randomized controlled trial(RCT). While the education program was found to increase engagement in the process of self-regulation and retirement from driving, this did not translate to reduced driving exposure between groups. Aim A nested process evaluation exploring relationships between program outcomes and quality of intervention implementation was conducted on ‘Behind the wheel’, a one-on-one education-based safe-transport program for older drivers. The process evaluation aimed: 1) to evaluate relationships between what was taught (treatment fidelity, timing of intervention and dose delivered), what was learnt (dose received), what was acceptable to participants (program acceptability) and what actually changed (treatment enactment/outcomes)(Bellg et al., 2004), 2) to explore participant characteristics of program uptake and 3) to explain the inputs, outputs and outcomes of our safe- transport program for older drivers. Methods We recruited 380 drivers aged 75 years and over from northwest Sydney to participate in a randomized controlled trial evaluating this program. Trial outcomes were stage of behaviour change measured by the Precaution Adoption Process Model and driving exposure measured objectively by in-vehicle monitoring. Process measures including program fidelity, acceptability, dose delivered and received were obtained from participant interview and educator notes. Relationships between process measures and program outcomes were explored using multivariate linear regression. A logic model was built from the data to explain the inputs, outputs and outcomes of this safe- transport program and relationships confirmed using logistic regression.