Effect of Two Lane Non-Urban Highway Geometry on Workload Profile of Drivers

Abstract

Transportation engineers play an important role to achieve zero- crash vision of the Government. The onus for occurrence of road crashes at under-designed and poorly constructed roads lies on the shoulders of transportation engineers. To ensure safe and comfortable driving, it is essential and necessary to evaluate the geometric design of roads, especially highways, from the perspective of the vehicle drivers. If the road is of consistent design, the driver can achieve smooth and safe driving. Inconsistent design of roads can confuse a driver and it may lead to unnecessary speed changes and even may result in unfavourable level of crashes. This paper attempts to study how the highway geometry affects the driver workload at horizontal curves and curves with gradient on two lane non-urban highways. The driver workload is assessed by measuring variations in physiological conditions of subject driver while driving in a test car under real field conditions. Heart rate (HR) and galvanic skin response (GSR) of drivers are continuously recorded using sensors attached to the driver’s ear and fingers respectively to develop a continuous profile of driver workload at varying highway geometry. The variations in heart rate from tangent sections to succeeding curve sections are determined to understand the effect of curve geometry on heart rate. The geometrical data such as radius of curvature, superelevation, sight distance, gradient and tangent length are collected from the selected study stretches. The study revealed that the inconsistent design of roads leads to large variations in heart rate and galvanic skin response. Consequently, crash frequency is found to be higher at such locations. The outcome of the study will help highway designers to design safer roads. The outcome of the study throws light on safety evaluation of highway geometry and will be helpful in developing tools and guidelines for designing safer roads.