Observations on the Horizontal Bends of Rural Roads Whose Plan Sheets Never Existed

Abstract

Unlike high-volume roads, for many low-volume country roads, curve advisory speeds cannot be predetermined in office because of the absence of plan sheets. In many places this is solely done by engineers on site using some degree of expert judgment, because conventional use of ball-bank indicators, as well as in-place radius and superelevation measurements for every horizontal curve, are time consuming. This is because of the high number of bends of such low-volume roads, a problem which is not fully acknowledged by many highway authorities. The present paper identifies common irregularities and inconsistencies concerning the horizontal bends of such roads based on the “continually” collected ball-bank data, as opposed to repetitive measurements. Three separate roads, located in the Afyon and Burdur regions in Turkey, each containing several horizontal curves, have been studied (two of them had no sheets of plans). The findings revealed that legal speed limits were inappropriate (even at tangents) and many curves did not have any speed signs, while some had unrealistic values being posted. The method described in this paper introduces a swift and reliable way of collecting information on how a vehicle negotiates these bends, so that problematic bends can be identified and later be revisited for further scrutiny.