Dixon, K. and R. Layton, The Influence of Human Factors on Access Management Design, 4th International Symposium on Highway Geometric Design (2010)
This paper addresses the influence of driver characteristics on the optimal access spacing, location, and design on roadway facilities. These characteristics include the drivers field of vision (based on perceived approach speed), visual ability, cognitive ability, mobility, and age and experience. To adequately consider the wide variation of these driver characteristics as they relate to specific access management decisions and unique contextual environments, the authors assess the effects of current design decisions, and how such assumptions contrast with human behavior-specific factors.
The authors explore the impact of human factors, such as sight distance, preview distance, object height, signing and marking, interchanges, lighting, medians, and driver expectancy, and how they may be further incorporated into design and control options. The paper describes how a constant perception-reaction time and deceleration rate are commonly used, yet the variation in facility function, speed, adjacent land-use, level of conflict, and transit/bicycle/pedestrian activity are excluded from direct consideration. The paper also cites the static height assumption currently made in determining stopping sight distances, arguing that for access management applications, object height could be represented better by vehicle headlight/taillight height or, for some situations, curb height (0.5 ft [150 mm]) or pavement surface (effectively an object height of 0 ft [0 mm]).
The concept of decision sight distance is appropriate for many access management applications since it directly reflects the increased level of complexity for different road environments. The author noted that even decision sight distance does not explicitly address the numerous and diverse characteristics common to the complex driving task and specific driver abilities.
The paper identified the following areas that would benefit from focused research efforts:
- Perception-reaction time for difference access management conditions and objects;
- Determination of workload measures for various conflicting conditions; and
- Determination of the impact of various street and driveway demand volumes on driveway location, spacing, and design.