The purpose of this study was to quantify the mental workload requirements and the limitations of human information processing capabilities of drivers in modern road traffic. In-car measurements using an instrumented car enable a detailed analysis of the behavior of the individual driver. The perceptible information of the outside environment (roadway, roadside environment) can be analyzed by measurements with video techniques. Such information was considered important in determining certain curve design criteria which would lead to effective safety and operational improvement at current curve sites. The data analyzed in this study included geometric, operational and physiological measures on road sections with different levels of difficulty. It was found that as curves become sharper, there is a proportionally greater increase in speed reduction and galvanic skin reaction. Other physiological measures, such as eye blink rate and variance of heart rate have shown a decrease in such curves. The study presents also an approach to combine operating-speed-based measurements and workload-based measurements for evaluating highway geometric design quality. The correspondence between the results of both measurements suggests that drivers oriented their driving behavior (e.g., speed, lateral guidance) besides others on their mental workload level. Appropriate curve design proposals for guidelines are discussed which may help to minimize potentially accident-related trends.
Abstract