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Operating Characteristics of the Segway™ Human Transporter

Chapter 1. introduction and Background

Statement of Problem

The Segway^TM Human Transporter (HT), shown in figure 1, is one of several low-speed transportation devices (e.g., bikes, scooters, and wheelchairs) that, under certain circumstances, travels on sidewalks, roadways, and other shared-use paths. The Segway^TM HT is a motorized device that can achieve a top speed of 12.5 mi/h (20.1 km/h). Riders operate the device in a standing position, which allows the Segway^TM HT to have a relatively small footprint. It is necessary to study riders' behavior under naturalistic sidewalk travel conditions to accommodate Segway^TM HT traffic. However, there is little prior research describing the operating characteristics of Segway^TM HTs under these conditions, and therefore, there is little empirical data to guide traffic engineers, planners, and policy makers.

Figure 1. Photo. A rider on a Segway^TM HT.

Research Goals

A Segway^TM HT rider has to manage speed, maneuver the device, pass a variety of objects, and stop in response to environmental stimuli including people, traffic signals, curbs, and obstructions such as light poles and park benches. The available empirical research on the Segway^TM HT is limited. Current literature offers some insight into several performance characteristics, including travel speeds, perception-reaction time, and braking distances. The goal of this research was to answer the following questions:

• What are typical travel speeds in each of the three speed limiting controls (operation keys)?
• How fast do riders approach obstacles?
• How do riders accelerate?
• How long does it take riders to stop the device?
• How close do riders come to obstacles?
• Do emergency stops differ from anticipated stops?
• Do novice riders operate the Segway^TM HT differently from experienced riders?

Background

The Segway^TM HT made its debut among a small group of users in 2001, and manufacturers began selling it to the general public in early 2003. It is marketed as a self-balancing transportation machine that runs on battery power and uses a combination of gyroscopes, tilt sensors, and computer processors to maintain balance. Table 1 lists the specifications of the i Series Segway^TM HT.

Table 1. Specifications of the Segway^TM HT i Series.⁽¹⁾

1 mi = 1.61 km 1 lb = 0.454 kg * Indicates that the speed limiting control keys act as a governor to limit the top speed of the Segway^TM HT.

Segway^TM HT regulations such as minimum age requirements; helmet use; and road, sidewalk, and trail use vary by State and community with some jurisdictions having no current regulations. According to the Governors Highway Safety Association, as of November 2008, 43 States and Washington, DC, have enacted legislation allowing the use of Segway^TM HTs, 5 States have no legislation, and 2 States have no statewide prohibitions.⁽²⁾

In 2006, the Consumer Products Safety Commission indicated that approximately 23,000 Segway^TM HTs were in operation.⁽³⁾ Although the actual number of Segway^TM HT riders is unknown, there is still a need to ensure safety. However, there is little available literature on the evaluation of Segway^TM HT usage or safety. Instead, a small number of papers have reported comparison evaluations of the Segway^TM HT among a larger class of personal transportation devices such as motorized scooters, wheelchairs, and bicycles. One issue that needs to be studied is how Segway^TM HT riders interact with other non-Segway^TM HT users on shared-use paths and roadways.

Some non-Federal Highway Administration (FHWA) literature has described the Segway^TM HT in the context of benefits and costs to individual riders and society. Liu and Parthasarathy provided an overview of the potential benefits of riding Segway^TM HTs (e.g., pollution reduction) and potential challenges (e.g., the cost of the device).⁽⁴⁾ Litman and Blair suggest features for characterizing different personal mobility devices, including the Segway^TM HT.⁽⁵⁾ They characterized the Segway^TM HT as having medium societal value, medium congestion impacts, and medium risk to others when compared to other nonmotorized devices such as individual walkers (high societal value), human-powered bicycles (medium to high risk to others), and equestrians (low societal value). They also suggest what is needed to manage nonmotorized facilities (where Segway^TM HT riders and other users mix), including determining regulations for mixed use, prioritizing users in terms of speed restrictions and yielding hierarchies, and developing education and enforcement policies. While their publication provides an overview of the potential problems associated with Segway^TM HTs in mixed-use settings, it is solely analytical and offers no empirical evidence for the values, impacts, and risks associated with Segway^TM HT use.

Other publications propose empirical research on devices including the Segway^TM HT. Shaheen et al. and Rodier et al. introduced the concept of the Segway^TM HT as a transportation connectivity device.^(6,7) They conducted a feasibility analysis and presented a plan for introducing low-speed modes of travel to users of California's Bay Area Rapid Transit (BART) system. They outlined the typical locations and types of crashes that occur for bicycles, scooters, skateboards, and wheelchairs. The authors concluded that, in general, 63 to 80 percent of low-speed crashes involve low-speed devices, and the highest rate of injury is among skateboarders at 2.15 injuries per 10,000 days of use. They concluded that among all of the modes studied, the risk of injury in low-speed travel is slight. While the Segway^TM HT is part of the proposed BART pilot program, no crash or injury statistics from its use were included in the analysis. This is understandable, given the novelty of the device, but it again confirms the need for empirical evaluation.

In an FHWA-sponsored study, Landis and his colleagues provided one of the few empirical analysis research efforts about Segway^TM HT usage.^(8,9) They conducted an experimental field study on trail users, including bicycle riders, in-line skaters, people pushing strollers, wheelchair users, Segway^TM HT riders, and others who were videotaped as they rode through a defined course. The researchers reported a comparative outline of pertinent operating statistics such as physical dimensions of the device, turning radius, speed, braking distance, etc. The results of the Segway^TM HT user performance are presented in table 2. Speed was defined as the normal cruising speed of users on a flat, smooth section of a shared-use facility. The perception-reaction time was defined as the duration between the researcher's commencement of the stop signal until the initiation of the braking action by the user. Unfortunately, these findings did not include speed key, which indicates the maximum speed that the Segway^TM HT can achieve. For the i Series, the black key is 6 mi/h (9.7 km/h), the yellow key is 8 mi/h (12.8 km/h), and the red key is 12.5 mi/h (20.1 km/h). Thus, it is unclear what speed keys participants used, making it difficult to assess the braking distance and speed data. However, the overall mean speed would indicate that a large percentage of the riders in the Landis et al. study employed the red key, which was the fastest speed. In addition, navigation around obstacles was not evaluated, and the study did not involve novice users.

Table 2. Segway^TM HT rider characteristics observed by Landis et al.^(8,9)

1 ft = 0.305 m 1 inch = 25.4 mm * Different than specified by Segway^TM LLC as shown in table 1.

Research Questions

The available empirical research on the Segway^TM HT offers a glimpse into several performance characteristics such as travel speed, turning radius, and braking distance. What is not as understood are the situations that riders frequently face in the real world and how they deal with those situations. To determine the most typical situations encountered by Segway^TM HT riders, a naturalistic review was conducted as a part of the present study. This review looked at the following sources of information:

• Segway^TM HT riders.
• Personal experience.
• Policy makers.
• Tour group operations.

The review was used to identify the most typical problems encountered in real sidewalk use by Segway^TM HTs. Real sidewalk conditions can be quite complex, and this complexity needs to be reflected in studies of rider performance to determine how the Segway^TM HT maneuvers in naturalistic settings. The present study investigates the behavior of Segway^TM HT riders and their performance in different operational situations.

The research questions addressed in the present study are as follows:

1. How fast do riders travel?
2. What speed do Segway^TM HT riders use when approaching obstacles?
3. How does speed affect braking distance and time?
4. How much time and distance does it take to complete a "planned" stop at a specified location?
5. How much time and distance does it take Segway^TM HT riders to respond to a signal when making an "unplanned" stop at the signal? How much time and distance does it take to complete the stop?
6. How much space (clearance distance) do Segway^TM HT riders use to navigate around obstacles?
7. How do Segway^TM HT riders pass pedestrians?
8. How does sidewalk width affect performance?
9. Does the performance of experienced Segway^TM HT riders differ from that of novice riders?

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