Characteristics of Emerging Road and Trail Users and Their Safety

Eye Height

The AASHTO Guide for the Development of Bicycle Facilities (p. 40) assumes a bicyclist eye height of 140 cm (54 inches) in calculating the minimum length of vertical curve necessary to provide minimum stopping sight distance at various speeds on crest vertical curves or sag vertical curves with overhead sight obstructions.⁽²⁾ Vertical curves are described in more detail in the Discussion section of this report. Table 7 shows that the mean eye height for bicyclists in this study was 157 cm (62 inches). The 85th percentile eye height for bicyclists was 150 cm (59 inches). In other words, 85 percent of bicyclists had eye heights of 150 cm (59 inches) or greater. Consequently, the AASHTO value seems conservative with the minimum values observed for bicyclists.

Hand cyclists appear to be the critical user for shared use path design of vertical curves, as they had the lowest mean (96 cm (38 inches)) and 85^th percentile (85 cm (33 inches)) eye heights. Among equipment types with five or more users, the 85^th percentile eye heights were less than 140 cm (54 inches) for users of the following: hand cycles, kick scooters, manual wheelchairs, power wheelchairs, and recumbent bicycles. The low eye heights for scooters may have been due to the users' ages.

^2. American Association of State Highway and Transportation Officials. Guide for the Development of Bicycle Facilities. American Association of State Highway and Transportation Officials, Washington, DC, 1999.

Table 7. Eye height.

NOTES:
1.This table includes only active participants.
2.AASHTO value for bicyclists = 140 cm (54 inches)
3.NA = Not applicable because N=1.