Optimal Application and Placement of Roadside Reflective Devices for Curves onTwo-Lane Rural Highways

摘要

A survey of the current delineation practices in the various U.S. States andCanadian Provinces indicated the importance of a set of quantitative delineation guidelines. According to the survey no U.S. State or Canadian Province uses computer assisted methods for the curve delineation task. A photolog analysis of the ODOT districts 5 and 10, with the objective to assess the usage of curve delineation across two ODOT districts, found that there is generally a good correspondence with regard to applying arrow signs. However, due to the practice of applying an arrow only, both districts do not provide as much curvature information as possible and desirable from a human factors point of view. The evaluator responses before and after curve delineation, with the objective to obtain input for the curve delineation tasks, indicate that (1) evaluators have difficulties to agree on the type, number, and location of curve delineation devices, just by looking at a curve while driving with low beams at nignt, (2) subjective evaluation of an undelineated curve tends to provide a recommended number of devices that is considerably lower than the actual number required when placing four devices within a driver's functional visual field of view, (3) the optimal type, number, an location of the delineation devices should be computed with a set of algorithms implemented in a software package. These findings support the development and use of a knowledge-based, interactive software which computes the delineation layout. The approach and center speed measurements before and after delineation installation were conducted in order to assure that there are no adverse effects on driver behavior due to delineation. The measurements indicate that there is no systematic pattern in speed increase or speed reduction before and after the delineation devices are installed.