To evaluate different vehicle designs, vehicle features, and the effects of changes or improvements made in vehicle designs, an ergonomics engineer should be able to measure and demonstrate how well the driver performs in different tasks while using the vehicle. Currently, there are very few standardized measures (or variables) and methods for measurement of driver behavior and driver performance. A number of researchers have used many different measures, and there is some agreement on the general approaches for performance measurements. However, many differences in de›ning even commonly used measures such as task completion times, variability in lane position, errors. exist due to differences in instrumentation, experimental procedures, and data collection techniques. Thus, the measurement problem occurs due to inconsistencies between researchers in determining what to measure and how to measure in any given driving or vehicle usage situation.