Development and evaluation of a Driving Observation Schedule (DOS) to study everyday driving performance of older drivers

•The Driver Observation Schedule (DOS) is a structured on-road driving task designed to observe individual driving behavior.•DOS was developed for use in the Candrive/Ozcandrive five-year prospective study of older drivers.•Preliminary findings show that DOS can be scored reliably, is of feasible duration, acceptable to drivers and representative of everyday driving.•DOS holds promise for quantifying and monitoring changes in older drivers’ performance in environments typical of their everyday driving. This paper describes the development and evaluation of an on-road procedure, the Driving Observation Schedule (DOS), for monitoring individual driving behavior. DOS was developed for use in the Candrive/Ozcandrive five-year prospective study of older drivers. Key features included observations in drivers’ own vehicles, in familiar environments chosen by the driver, with start/end points at their own homes. Participants were 33 drivers aged 75+ years, who drove their selected route with observations recorded during intersection negotiation, lane-changing, merging, low speed maneuvers and maneuver-free driving. Driving behaviors were scored by a specialist occupational therapy driving assessor and another trained observer. Drivers also completed a post-drive survey about the acceptability of DOS. Vehicle position, speed, distance and specific roadways traveled were recorded by an in-vehicle device installed in the participant's vehicle; this device was also used to monitor participants’ driving over several months, allowing comparison of DOS trips with their everyday driving. Inter-rater reliability and DOS feasibility, acceptability and ecological validity are reported here. On average, drivers completed the DOS trip in 30.48min (SD=7.99). Inter-rater reliability measures indicated strong agreement between the trained and the expert observers: intra-class correlations (ICC)=0.905, CI 95% 0.747–0.965, p