Research was conducted to assess driver acceptance and performance associated with a spotter mirror feature intended to reduce the incidence of lane-change conflicts by enhancing drivers' ability to detect vehicles in their side blind zone. The spotter mirror consisted of an integrated spherical convex blind zone mirror inset within a larger planar mirror. The spotter mirror's field-of-view was designed to target the vehicle's side blind zone area and to help drivers quickly detect the presence or absence of a vehicle in the blind zone. The study captured normative lane-change behavior during an extended drive on public roadways, with and without access to the spotter mirror system, for a sample of familiar and unfamiliar supplemental mirror users. In order to capture more naturalistic lane-change behavior, drivers were informed that the purpose of the study was to evaluate the adequacy of existing road signs for navigating to a destination. The study also allowed performance under critical conflict situations to be evaluated by adopting the unique approach of using a confederate vehicle to stage conflict situations at designated points along the drive. Results found that access to the spotter mirror increases mirror sampling under critical situations where a vehicle is in the blind spot area. No evidence was found to suggest that use of the spotter mirror increases any inherent risk associated with performing lane changes.