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Publication Number: FHWA-HRT-04-104
Date: September 2004
Characteristics of Emerging Road and Trail Users and their Safety
FHWA Contact: Ann Do,
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Throughout the United States, the varieties and numbers of nonmotorized devices used on trail and roadway facilities have increased dramatically. People using kick scooters, in-line skates, hand cycles, recumbent bicycles, and other emerging devices compete for space with bicyclists and pedestrians. Urban trail operators report operational and safety problems associated with the increasing number of emerging users and their operational needs. User groups are petitioning State legislatures and local governments for permission to operate on roadways legally.
The standards in the American Association of State Highway and Transportation Officials (AASHTO) Guide for the Development of Bicycle Facilities, which are based on the physical dimensions and operating characteristics of bicycles, may not meet the needs of emerging trail users. To address this issue, the Federal Highway Administration (FHWA) sponsored a study to better understand the physical dimensions and operational characteristics of an increasingly diverse group of nonmotorized trail and roadway devices. They include the following:
Design professionals can use the results of this study to design roadway and shared-use path facilities to meet the operational and safety needs of this growing and diverse group of users.
Field data collection activities were conducted using bicycles and emerging devices at 21 data collection stations at three shared-use paths across the United States. The individual event locations were planned and advertised as "Rides for Science" to encourage participation by targeted user groups. Events were held at the San Lorenzo River Trail in California, the Pinellas Trail in Florida, and the Paint Branch Trail in Maryland. These "Ride for Science" events included 811 participants.
Seven data collection stations were setup at each trail. Collected data included the following:
Physical characteristics and three-point turn widths were measured and video cameras were setup to record participants' movements at various locations along the trails. Following each data collection event, the videotapes were converted to digital format and subsequently viewed to reduce the data and determine operational characteristics for each data collection station.
The research confirmed a great diversity in the operating characteristics of various road and trail user types. Furthermore, the research determined that it might be prudent to use an emerging user device instead of the bicycle as the design vehicle for shared-use paths or nonmotorized roadway facilities. Some examples of findings that suggest this variable design user approach follow:
Sweep Width. The AASHTO Guide for the Development of Bicycle Facilities recommends a minimum path width of 1.2 meters (m) (4 feet (ft)) for bike lanes and 3 m (10 ft) for shared-use paths.
Design Speed. AASHTO specifies 30 kilometers per hour (km/h) (20 miles per hour (mi/h)) as a minimum design speed on shared-use paths.
Horizontal Alignment. AASHTO recommends a minimum horizontal curve radius of 27 m (90 ft) for cyclists traveling at 30 km/h (20 mi/h) around a curve with a 2 percent superelevation.
Stopping Sight Distance. The required stopping sight distance of users depends on their travel speed, eye height, reaction times, and deceleration capabilities. AASHTO recommends a stopping sight distance of 38.7 m (127 ft) for a bicyclist traveling at the recommended design speed of 30 km/h (20 mi/h) on wet pavement.
Vertical Alignment/Crest Vertical Curves. The minimum length of a crest vertical curve depends on the user's stopping sight distance and eye height and the algebraic change in grade. Given a 10 percent change in grade, AASHTO's minimum length of a crest vertical curve for a bicyclist with its presumed 38.7-m (127-ft) stopping sight distance is 49.8 m (163 ft).
Refuge Islands. Refuge islands are provided between opposing motor vehicle traffic flows to allow pathway users to cross only one direction of traffic flow at a time. The AASHTO Guide for the Development of Bicycle Facilities states that a refuge island width of "2.0 m (6 ft) is poor, 2.5 m (8 ft) is satisfactory, and 3.0 m (10 ft) is good."
Signal Clearance Intervals. Yellow plus all-red intervals for motor vehicles typically are 5 seconds or less.
Pedestrian Clearance Intervals. Pedestrian clearance intervals are intended to allow pedestrians who begin crossing a signalized intersection any time before the beginning of the flashing "DON'T WALK" phase to completely cross the street before crossing traffic enters the intersection. Typically, pedestrian signals are timed for walking speeds of 1.2 meters per second (m/s) (4 feet per second (ft/s)). The manual wheelchair users evaluated were able to cross intersections within the time provided for an assumed 1.2-m/s (4-ft/s) walking speed.
Segway User Characteristics. Based on the performance of the five Segways evaluated in the study, a Segway user would not be the critical user for any of the design criteria evaluated.
The following chart represents potential facility design criteria and design users based on the FHWA study:
While additional research is needed to determine which devices should be used to set specific design criteria, the findings suggest that design guidelines might 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 and diverse group of users.