Reliability and Validity of the Closed-Course Version of the Standardized On-Road Assessment for Drivers (SOAD) With People With Mild Stroke

Abstract

Importance: Driving assessments are essential in occupational therapy for people with brain injuries. On-road evaluations are considered the gold standard, yet ensuring their psychometric rigor remains a challenge.

Objective: To evaluate the reliability and validity of the closed-course version of the Standardized On-Road Assessment for Drivers (SOAD) using both classical test theory and item response theory (IRT) approaches.

Design: Psychometric study integrating factor analysis and IRT.

Setting: Five rehabilitation hospitals and associated driving schools in Japan.

Participants: A total of 108 patients with mild stroke, referred by physicians for driving evaluation. All participants completed off-road screening before the SOAD closed-course assessment.

Outcomes and measures: Psychometric properties were examined across five domains: item validity, structural validity, discriminant and convergent validity, internal consistency reliability, and item response. Data were analyzed using exploratory and confirmatory factor analyses and IRT.

Results: Factor analysis reduced the original 40 items to 16 and identified five factors: basic skills, driving attitude, scanning outside the field of view, hazard prediction, and merging. Internal consistency reliability was acceptable (α = .657-.829). Convergent and discriminant validity were supported by average variance extracted values (.482-.877) and squared correlations. IRT showed appropriate item discrimination (.386-.829) and difficulty (-2.508 to .113).

Conclusions and relevance: This study supports the reliability and validity of the SOAD closed-course version. The tool may be particularly useful in settings with legal constraints on public road driving assessments. Plain-Language Summary: Driving after a stroke can be difficult, and deciding whether someone is ready to drive again is an important part of occupational therapy. This study examined a tool called the Standardized On-Road Assessment for Drivers (SOAD), which tests driving ability on a safe, closed driving course. The study included 108 people who had experienced a mild stroke. Researchers used statistical methods to check whether the SOAD gives consistent and accurate results. They found that the tool measures five important driving skills and can tell how well someone is performing in each area. These findings mean that therapists can use the SOAD to better understand their clients' driving abilities and make safer decisions-especially in places where driving on public roads is restricted during assessment. This research helps make driving evaluations safer and more reliable for people recovering from mild brain injuries. The SOAD closed-course version was found to be a reliable and valid on-road test. This on-road test can adequately assess the driving ability of people with mild stroke in some regions and situations.