Characteristics of Emerging Road Users and Their Safety

Federal Highway Administration


"This study was undertaken to clarify the operational characteristics of an increasingly diverse group of trail and other nonmotorized transportation users. Three "Ride for Science" data collection events were conducted to obtain the physical dimensions, turning capabilities, lateral operating space, acceleration, speed, and stopping sight distance of trail users. The results confirmed the great diversity in the operating characteristics of various road and trail user types. Some examples of findings include:

  • Sweep Width -- The 85th percentile inline skater had a 1.5-meter (m) (4.9-foot (ft) sweep width, wider than the AASHTO recommended width for bike lanes.
  • Design Speed -- Recumbent bicyclists had the highest observed 85th percentile speeds of 29 kilometers per hour (km/h) (18 miles per hour (mi/h)), less than AASHTO's minimum design speed.
  • Horizontal Alignment -- Most users did not reduce their speeds for turning radii greater than 16 m (52.5 ft).
  • Stopping Sight Distance -- A recumbent cyclist in the 85th percentile requires a stopping sight distance of 32.7 m (107.3 ft) on wet pavement, less than the AASHTO value.
  • Vertical Alignment/Crest Vertical Curves -- Recumbent bicyclists had a required length of a crest vertical curve of 46.7 m (153 ft), less than the AASHTO value.
  • Signal Clearance Intervals -- Five-second clearance intervals would provide insufficient time for most users (85th percentile users) to clear a five-lane (18.3-m (60-ft) wide) intersection.
  • Characteristics of Segway┬« Users -- Many characteristics of Segway users were comparable with those of other emerging trail users.

"These findings suggest that design guidelines may need to be revised to incorporate the needs of emerging trail users. The results of this study can be used to help design professionals adequately design roadway and shared use path facilities to meet the operational and safety needs of this growing group of users."

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Filed in: Engineering, Plans and Policies, Crashes and Safety

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