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Operating Characteristics of the Segway™ Human Transporter

Chapter 4. Discussion and Recommendations

The objective of this study was to conduct an empirical assessment of several operating characteristics of the Segway^TM HT. Specifically, the operating characteristics of interest were as follows:

• Travel speed of experienced Segway^TM HT riders.
• Approach speed of experienced and novice Segway^TM HT riders in the presence of obstacles.
• Acceleration of experienced Segway^TM HT riders.
• Stopping distance of experienced Segway^TM HT riders.
• Clearance distance of experienced and novice Segway^TM HT riders in the presence of obstacles.

Discussion

Participants comfortably traveled near the top speed allowed by each speed key (i.e., black, yellow, or red). Also, as would be expected, speed was the dominant factor in determining the distance it took for participants to stop. The faster the riders were traveling, the more distance it took them to initiate and complete a stop. When stops were unplanned, riders' response times were approximately 0.5 s with an SD of 0.2 s. Using a different data collection methodology, Landis et al. observed a mean perception-reaction time of 1.1 s with an SD of 0.6 s.^(8,9) In the Landis study, a stop sign was used, and the participants were told that a stop might occur. In this study, a stop signal was used, and participants were told that a stop would occur. Although participants did not initially know when to stop in the unplanned trials, they were aware that a stop would be required at some time during the trial. Some braking distances were long; unplanned stops while traveling near top speed in the red key required on average 21 ft (6.4 m).

This study was designed to answer the nine basic questions concerning characteristics of Segway^TM HT riding behavior posed in the introduction. For the given experimental procedures and test course, the results of the study revealed the following:

1. Experienced Segway^TM HT riders traveled at a mean speed of about 5.75 mi/h (9.26 km/h) in the black key, 7.71 mi/h (12.4 km/h) in the yellow key, and 11.2 mi/h (18.0 km/h) in the red key.
2. Novice and experienced Segway^TM HT riders approached obstacles at a mean speed of about 4.5 mi/h (7.2 km/h) with a range from 2.7 mi/h (4.3 km/h) to 6.8 mi/h (10.9 km/h).
3. Experienced Segway^TM HT riders passed obstacles faster than novice riders by about 1.9 mi/h (3.1 km/h) on average.
4. Novice and experienced Segway^TM HT riders passed moving pedestrians at an average speed of about 5 mi/h (8.1 km/h) and with an average clearance of 35.9 inches (911.9 mm).
5. Novice and experienced Segway^TM HT riders passed obstacles slower by about 0.5 mi/h (0.8 km/h) on average and at closer distances by about 17.6 inches (447.0 mm) on average on a narrow sidewalk as opposed to a wide sidewalk.
6. Experienced Segway^TM HT riders made planned stops in a mean time of about 2.42 s with a range from 2.21 s to 2.64 s and at a mean distance of about 10.2 ft (3.1 m) with a range from 6.36 to 15.2 ft (1.94 to 4.64 m).
7. Experienced Segway^TM HT riders' response times for unplanned stops took a mean time of about 0.52 s while traveling a mean distance of about 5.36 ft (1.63 m). Riders completed the braking portion of the unplanned stops in a mean time of about 1.79 s while traveling a mean distance of about 9.10 ft (2.78 m). The total mean stopping time took 2.31 s while traveling a total mean distance of about 14.5 ft (4.42 m).
8. Experienced Segway^TM HT riders stopped while operating the Segway^TM HT in the black key at a mean distance of about 5.5 ft (1.7 m) with a range between 3.7 and 8.2 ft (1.1 and 2.5 m), in the yellow key at a mean distance of 8.7 ft (2.7 m) with a range between 7.1 and 13.2 ft (2.2 and 4.0 m), and in the red key at a mean distance of 14.7 ft (4.48 m) with a range between 12.5 and 18.8 ft (3.8 and 5.7 m).
9. Novice and experienced Segway^TM HT riders passed obstacles with a mean clearance of about 14.5 inches (368.3 mm) with a range from 3.3 to 43.2 inches (83.8 to 1,097.3 mm).

The findings reported herein are some of the first efforts to examine the performance of Segway^TM HT riders with respect to speed, braking, and maneuverability. However, this study is not without its limitations. Participants were not operating in a fully natural environment. They were making repeated trips on a relatively straight sidewalk under fair weather conditions with either no obstacles or a limited number of relatively forgiving obstacles. For ethical reasons, all obstacles minimized risk for the Segway^TM HT riders. The obstacles were all made of standard temporary traffic control hardware, which moves easily in a collision. These cones, barrels, and barriers did not pose as strong a collision threat as a fixed object like a tree or concrete barrier. For similar safety reasons, the walking pedestrian obstacles were experimenters aware of the Segway^TM HT presence and trained in how to avoid a collision. These staged pedestrian/ experimenters would not be likely to exhibit startled reactions or other possible naturalistic behaviors as might be observed with the general public, especially if a Segway^TM HT approaches from behind. For similar safety reasons, these staged pedestrians were allowed only on the wide sidewalk and not on the narrow sidewalk.

Participants did not have to move backwards or frequently adjust their speed during the experimental trials. They were observed continuously, and some of their behavior could have been shaped by researcher expectations. Finally, the sample group of Segway^TM HT riders was relatively homogeneous, composed of experienced and enthusiastic Segway^TM HT users and novice riders chosen from the Washington, DC, area. Since novice riders were being tested, the Institutional Review Board required special safety considerations such as one-on-one training for novice riders. Additionally, minors under the age of 18 were not permitted to participate.

There were other limitations in the experiment as well. There were no convenient narrow sidewalks of sufficient length at the testing site, so the narrow sidewalk condition had to be produced by applying white tape boundary markings to a separate section of the wide sidewalk. This represented a somewhat forgiving width restriction, possibly contributing to faster speeds. In addition, the wide and narrow sidewalk test sections were not long enough for some riders to achieve maximum travel speed, even in the yellow speed key. Therefore, the speed values may be somewhat underestimated. To the degree that clearance distances are correlated with travel speed, the observed clearance distances may not be representative of what might be obtained under different conditions. Moreover, the wide and narrow sidewalk test sections were relatively short and close to each other. In addition, some of the obstacles were placed in relatively close proximity to each other, creating a rather constrained overall sidewalk environment. For example, on the wide sidewalk, the barrel had a higher approach speed than the cone, which is an unintuitive result. This outcome may have been the result of the barrel being placed in a straight section of the sidewalk and the cone in a curved section of the sidewalk path. In general, rider behavior for one obstacle may have been affected by the preceding or subsequent obstacle or path. Somewhat different results might be obtained in a more open and expansive sidewalk environment where isolated obstacles were few and far between. Lastly, this study provides no information about individual characteristics that influence Segway^TM HT performance such as age, fatigue, etc. Future work should investigate Segway^TM HT travel in a more naturalistic setting where participants have more freedom to control the pace and route that the Segway^TM HT travels.

Recommendations

As previously indicated, the widths of the narrow and wide sidewalk test sections were 4.4 ft (1.3 m) and 10.2 ft (3.1 m), respectively. AASHTO recommends a 4-ft (1.2-m) minimum clear sidewalk width.⁽¹²⁾ However, AASHTO also recommends that sidewalks less than 5 ft (1.5 m) should have passing space of at least 5 ft (1.5 m) at reasonable intervals.⁽¹³⁾ ADAAG states that 4 ft (1.2 m) is the minimum width for a wheelchair and one ambulatory person to pass each other.⁽¹¹⁾ The narrow sidewalk width employed in the present experiment was between these two values.

Novice and experienced Segway^TM HT riders encountered pedestrians only on the wide sidewalk. The Segway^TM HT riders passed one pedestrian per experimental trial for a total of six trials. Three trials involved a pedestrian walking towards the Segway^TM HT (opposite direction), and three trials involved a pedestrian walking with the rider (same direction). Across the 20 novice and experienced participants, these 6 trials resulted in a mean lateral passing clearance distance of about 3 ft (0.9 m). This clearance distance was considerably larger than the mean lateral clearance (1.2 ft (0.4 m)) for the inanimate stationary obstacles used in this study. If the width of the Segway^TM HT (2.1 ft (0.6 m)) and the width of the pedestrian (about 2.0 ft (0.6 m)) are taken into consideration, the average passing event involving the Segway^TM HT rider and the pedestrian required a minimum total distance of approximately 7.0 ft (2.1 m). If similar results occurred on a real sidewalk in the field, Segway^TM riders and pedestrians could face potential problems passing each other on city or suburban sidewalks that were built to the minimum AASHTO or ADAAG recommendations. AASHTO suggests that widths of 8 ft (2.4 m) or greater may be necessary in certain commercial areas.⁽¹²⁾ Based on the results of this study, widths of 8 ft (2.4 m) or greater should adequately accommodate Segway^TM HT and pedestrian passing events. It is not certain how a pedestrian and a Segway^TM HT rider would negotiate for passing space on a narrower sidewalk or how a Segway^TM HT would interact with wheelchairs, bicycles, or other novel transport devices.

Overall, the results of this study indicate that experienced Segway^TM HT riders were capable of stopping for both planned and unplanned stops. Both novice and experienced Segway^TM riders were capable of traversing past the various obstacles on the two test sidewalks without major difficulties. The controlled test courses attempted to simulate several typical conditions that a Segway^TM HT rider might commonly encounter in the real world. The testing environment was somewhat artificial (e.g., limited pedestrian activity, clean and smooth riding surface, etc.) compared with what might typically exist in the real world. Nevertheless, the study produced results that might serve as an empirical foundation for additional field research which could subsequently be conducted under more varied and realistic conditions. The results provided needed empirical data regarding the operating characteristics of the Segway^TM HT as related to acceleration and stopping distance (both planned and unplanned) as well as approach speed and clearance distance when navigating around obstacles. Such information could be useful for developing a rational approach to incorporate Segway^TM HT traffic into the regulation, planning, designing, and controlling of shared-use paths and roadways. The Segway^TM HT represents just one of many novel, unconventional transportation modes that may share these facilities in the future. The methodologies described herein may prove useful in determining the operating characteristics of these other novel modes, as well.

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