Page 97 - Highway Engineering Handbook Building and Rehabilitating the Infrastructure
P. 97
80 CHAPTER TWO
FIGURE 2.6 Horizontal sight distance along curve. Conversion: 1 ft 0.305 m. (From Location and
Design Manual, Vol. 1, Roadway Design, Ohio Department of Transportation, with permission)
When a cut slope is the potential restriction, the offset should be measured to a point
on the backslope having the same elevation as the average of the roadway where the
driver is, and the location of the lane downstream where a potential hazardous object lies.
In this way, an allowance of 2.75 ft (0.84 m) of vegetative growth on the backslope can
be made, since the driver’s eye is assumed to be 3.5 ft (1.07 m) above the pavement and
the top of a 2.0-ft (0.61-m) hazardous object downstream may still be seen.
Vertical sight distance may be restricted by the presence of vertical curves in the
roadway profile. The sight distance on a crest vertical curve is based on a driver’s
