1. Introduction

As older people start to have difficulty in walking many choose to use a mobility scooter to help them move around. Benefitting from improved design, mobility scooters are becoming an increasingly popular mobility device and are a common sight on many streets. However, very little is known about their usage or their impact in terms of either quality of life or functional health. Whilst mobility scooters may help to improve the quality of life of their users, it is also possible that the sedentary nature of their usage results in a decline of physical functionality and therefore reduced capabilities. Before any substantial research can be carried out it is crucial to understand the importance of a mobility scooter on the lives of the people that use them and to review the initial research published on the effect of scooter use on physical health. This paper is a state-of-the-art review. It describes the current research knowledge on mobility scooters, shows where gaps in knowledge exist and where future research needs to focus.

Every year every person makes an average of 923 journeys, 22% of these are by foot . The health outcomes of active transport, such as walking are widely acknowledged.  Many older people have difficulty in walking and the percentage of people in this group rises with age . Depending on the reasons behind the difficulty, as people begin to struggle to walk they have a range of options open to them which can be used alone or in combination. They can; walk less often, walk less far, take more frequent rest breaks while walking, use public or private transport, use a mobility aid for stability such as a walker or a cane, or use a mobility device instead of walking such as a wheelchair or a mobility scooter.

Mobility scooters are becoming an increasingly common sight on many streets. Benefitting from improved design and image as well as a decrease in usage stigma, mobility scooters have become an increasingly popular mobility aid. They can be hired in large supermarkets, in shopping centres, at some tourist attractions and visitor centres and are widely available for purchase including on the high street. However, despite their prevalence little is known about their impact upon their users physical health and physical capabilities.

From a health literature perspective a mobility scooter can be seen as a walking and physical activity replacement. It enables its user to travel distances they previously would have made by foot (or short distance vehicle trips) without any physical effort. For some older people a mobility scooter can be a replacement for a car and for the types of trips they would have made with a car. However a mobility scooter also has the potential to replace shorter trips that car drivers might previously have considered too short to drive, and therefore would have walked. For an older adult with difficultly maintaining their previous levels of walking, using a mobility scooter allows them to participate in activities they previously could not access, to participate in activities without discomfort or to extend the duration of participation.

The evidence supporting the health benefits of physical activity for older adults is well documented. On the one hand, the mobility scooter, as a sedentary mobility device may plays a detrimental role in the health of its user. On the other hand, the popularity of the device suggests that there are great benefits to its use. It is important to understand the role mobility scooters plays in older people physical health so that we can ensure older people who use scooters get the greatest benefits without risking their future physical functionality. Before any substantial research can be carried out to untangle the complexity of the impact mobility scooter usage has on physical health it is crucial to understand the importance of a mobility scooter on the lives of the people that use them and to review the initial research published on the effect of scooter use on physical health.

This paper is a state-of-the-art review of the current literature available. It examines where knowledge gaps lie and where future research is and should be focussed.

2. Background

Mobility scooters are a single occupant electronic transport vehicle and are used as a mobility aid. A solely battery operated device; it usually has between three and five wheels and is steered using a handlebar. Different scooters can be ridden either on the pavement or the road depending on speed capability and they may include a horn, lights and space for storage. They are often referred to as power-operated vehicle/scooters or electric scooters. Mobility scooters are designed for and used by individuals who are able to walk and manipulate themselves on and off a seated object. Unlike wheelchairs, mobility scooters are generally treated as vehicles in the sense that they do not have to be guaranteed access into buildings. This means that in order to access services and activities users must be able to walk.

In the United Kingdom () there are numerous ways to access mobility scooters. Many retail outlets sell them, including a major high street seller, specialist retails stores and multiple online providers. Additionally, they are bought second-hand. Many loan schemes for mobility scooters exist. Although the National Health Service (NHS) does not provide patients with scooters some local councils, for example operate a long-term loan scheme and short-term hire schemes. Some large supermarkets loan scooters to shoppers free of charge while they are on the premises. The largest scheme giving access to mobility scooters is Shopmobility. Shopmobility is a lending scheme based in shopping areas who lend mobility scooters, powered wheelchairs and manual wheelchairs to people whilst they are in the shopping district. Charging for use varies but most schemes are free. The service is offered to anyone who is permanently or temporarily disabled though no proof is required making the scheme essentially available to be used by anyone. Users must become members of the scheme and training on usage is offered at this stage. Once a member bookings can be made in advance of arrival.

Scooters are defined as class two or class three vehicles. No driving licence is required to operate them. Both classes of vehicle must be driven by people who are disabled and are 14 or older. However it is not clear whether these rules are being enforced in class two mobility scooters. Class three vehicles must be registered with the Driver and Vehicle Licensing Agency (DVLA), although they do not pay road tax they do have to display a NIL tax disk. Class two scooters are those that cannot exceed 6.44 km/h (4 mph), can be used on the pavement and cannot be used in the road except where crossing it. Class three scooters can travel up to 12.9 km/h (8 miles). They are allowed by law on the road if they are travelling at greater than 6.44 km/h but must not travel on motorways. Class three vehicles must have lights, mirrors and a horn.

<>The mobility scooter is considered to be an assistive technology. Assistive technology is defined by the World Health Organisation (2004) as any device or system that allows individuals to perform tasks that they would otherwise be unable to do or increases the ease and safety with which tasks can be performed. In order to carry out the desired activities, for example visiting family or going shopping, users need the physical functionality mentioned above. Safe operation of the scooter also requires the user to be able to turn their head to look behind them, although class three scooters, and some class two scooters include rear view mirrors. Safe operation also requires the ability to balance when the scooter is driving on a slope, on rough grounds or on and off pavements. Despite the necessary physical functionality when moving on and off the mobility scooter, the actual operation is a mainly passive task, requiring only a minimal amount of grip strength to engage the accelerator. In this sense the scooter does not assist the user to walk but removes the necessity of the task (at least while on the scooter).

Mobility scooters are an entirely optional device. A mobility scooter has not been designed, nor has built the environment infrastructure been altered to allow for mobility scooters to access most buildings. Therefore, a person using a mobility scooter needs to be able to walk albeit for short distances and/or with assistance. Whereas wheelchairs, electric or manual, are provided by the National Health Service (2014) (NHS), the choice to use a mobility scooter is made by the individual. Mobility scooters are bought privately, although a registered disabled person can apply for a small subsidy.

3. Methodology

This review examines the current knowledge of mobility scooters in relation to the effects they have on the user, in particular the user perspective of their device and any changes to the physical health of the user. In this case physical health is referring more specifically to physical functionality of mobility in the users over time, i.e., the maintenance of their capabilities of walking at the level they could before they began to use a scooter. Emphasis has been placed on older people, as one of the most visible users Barton et al., 2014 and the group of people more likely to become frail Rockwood. Older people is a term which can range in meaning from all those above 60 years old to an older subset of this group or simply those of pensionable age Gilleard and Higgs, 2011; Roebuck, 1979; United Nations, 2002; Victor, 2010. Some studies make no mention of age, where the focus is on the injury, disability or capability of the user.

In gathering the evidence this paper includes papers and reports with a variety of research designs, including both larger controlled trials and smaller case studies, using either qualitative or quantitative methods. Literature was identified by searching electronic databases, SCOPUS, PubMed, PsychINFO, EMBASE and AMED. The search terms used were: mobility scooters, electric scooters, motoris(z)ed scooters, and powered mobility devices. The reference lists of relevant papers were examined to locate any secondary sources not gathered through the original search. Government websites (Department for Transport, Office for National Statistics and Department of Health) were searched for relevant statistics, reports or policy documents. The criteria for inclusion was (1) primary source studies, (2) studies involving adults (3) studies which included outcomes for mobility scooter users as separate from other personal mobility devices and (4) studies presented in English. The articles were then filtered to remove irrelevant papers (for example, papers on childrens push scooters and mopeds). No papers were found on accidents involving scooters with the exception of media publications which were not included as they recounted singular accidents with little objective evidence.

Literature on mobility scooters can be divided into three categories, (1) prevalence within the population, (2) user perspectives and (3) physical functionality and physical capability impact.

There is a dearth of literature on mobility scooters. Where it does exist it is often research in combination with and undifferentiated from electric wheelchairs. Like scooter users, many manual wheelchair users have some physical functionality that allows them some mobility Hoenig et al., 2002. However, whilst a useful starting point the evidence from these studies will not always be relevant to scooter users. electric wheelchairs are only provided on the NHS to those people who need wheelchairs fulltime and are unable to propel themselves in a manual wheelchair Standards for Better Health, 2005) unlike a mobility scooter, which is a private purchase. To gain a wider understanding of what may be relevant to mobility scooter users, some evidence on wheelchairs have been included here. Where evidence relates only to scooters this has been made apparent.

4.1. Prevalence

There have been many attempts to quantify the number of mobility devices, particularly wheelchairs, in different countries. This data would be useful to help to understand the population who use them and to follow any trends in prevalence and their impact. Due to limited registration requirements and a lack of clear differentiation between mobility scooters and wheelchairs, accurate numbers are not available. However, some estimates of numbers and evidence of trends do exist.

4.1.1. Wheelchairs

The number of wheelchair users has increased. Evidence has been found that between 1986 and 1996 the number of wheelchair users doubled. Current figures for wheelchair use are estimated at 1.2 million, with 825,000 of those being regular, long term users.

4.1.2. Mobility scooters

Mobility scooter numbers are less well documented than wheelchair numbers. Where documented they reflect wheelchairs in their increasing numbers. In 2009 the sales of mobility scooters totalled 83 million but this had increased to 96 million in 2013. This rise is reflected in global figures of 182 million in 2009 rising to an estimated 245 million in 2013. Projected estimates for 2017 global sales reaches 335 million. In 2006 it was estimated that around 25,000 mobility scooters were bought each year and it is now estimated that approximately 80,000 are being bought each year. An estimated 350,000 are currently being used. Ricability׳s survey found that 47% of their mobility scooter respondents were over 65, lower than the estimated 74% of wheelchair users over 60. Using the estimate population data, percentages of users can be calculated. 1.5% of the population over 65 uses scooters compared with 0.5% in the general population. This percentage is similar to who used the English Longitudinal Study of Ageing database (ELSA) to discover the proportion of over 65 year olds who use mobility scooters. ELSA included a question on mobility scooter use (rather than ownership).  examined a subset of ELSA and found 1.4% of those aged over 65 used a mobility scooter.

Whilst the use of mobility devices including mobility scooters is increasing there is no evidence that the number of people with difficulty walking has increased. For example, US research shows that the number of people unable to walk 400 m (quarter of a mile) has not changed over time. LaPlantes data is from across all ages and they state that the data does not shown clearly whether increases in mobility device use is down to older people or non older people. It has been suggested that the growth in usage is down to a decrease in usage stigma and improved device image and design.

4.2. User perspectives

Studies on user perspective or user experiences are crucial to ensuring mobility scooters meet their users requirements and highlight where improvements can be made. Whilst studies on different aspects of user perspective exist on assistive technology devices only two studies have focussed solely on mobility scooters and their users.

4.2.1. Person-device match

The unregulated access to assistive mobility devices including mobility scooters, while giving potential users freedom of choice, does have a disadvantage. It means a lack of good advice to assess the suitability of a device to a person and vice versa. There is a great need for an assistive technology device to match an individual׳s capability/mobility needs. When a device is matched correctly the device is seen by the individual as empowering and giving them more freedom. When the device does not suit them users lack confidence and are at higher risk to their own safety.

4.2.2. Training and guidance

The amount of training given to users influences their likelihood to use the device. Whilst there is support for training for safe use training does not always occur. Estimates of the number of scooter users who receive training vary widely. An international survey of scooter users found only 25% had received training. However, a study found that a majority of users, 59%, received training, with 42% of users receiving the training from the organisation they bought their scooter from. A focus group of scooter users and stakeholders recognised that there were safety risks involved in using scooters but there is no data to prove this. Training does occur but is not available at a national level. Local schemes are often run by the police or mobility centres run a scheme in Yorkshire.

Only a third of wheelchair and mobility scooter users ask for guidance from a health professional before buying their device. some advice is available. Disability Rights , a disability network, provides an online guide to the range of scooters available and some guidance on how to choose the right one for individual needs Ricability, a consumer research charity, creates independent reports for older and disabled people on various assistive technology goods. They have a guide on using mobility scooters on public transport and choosing the right scooter ).

4.2.3. Satisfaction, independence and wellbeing

Research around user satisfaction, independence and wellbeing specifically of mobility scooters is sparse. With the exceptions of two papers, any research on mobility scooters in these areas is combined and undifferentiated with electric wheelchairs.

Studies of a range of assistive mobility devices for mobility found that users felt their device enabled them to participate in more activities, gave them greater independence and increased their sense of security. Evidence specifically from mobility scooters show that users generally view their devices positively, associating them with the freedom to move independently outside the house, in some cases being housebound without them.

A small study of powered wheelchair and scooter users found a high level of satisfaction and ease in activity participation after uptake of their devices. Users found that their ability to socialise, be mobile and their sense of safety, independence and self-esteem all raised as a result of device uptake. The studies findings are limited by its small sample size (20 mobility scooter users and 4 electric wheelchair users) and its lack of differentiation in its results between the different types of user by device. However, given that 80% of the sample are scooter users it can be concluded that scooter users do gain satisfaction, security and independence from using their scooter.

Barton et al. (2014) surveyed a total of 480 mobility scooter users of all ages . It is the first large survey of scooter users . The survey gives some useful insight into scooter user satisfaction and travel behaviour. This was a self-selecting sample of users, the majority of whom, 88%, owned their own scooter. Respondents were asked why they chose to use a mobility scooter, instead of a wheelchair. The two most common responses were that scooters were easier to use (61%) and that scooters were more comfortable (52%). In addition they found that users relied on their scooter to get around, with 74% of respondents saying they would not make the same trips without their scooter. Of those who felt they could make the same trips without the mobility scooter only 10% felt they could make the trip by walking.

May et al. (2010) surveyed a total of 66 scooter users and held focus groups with an additional 15 users. The research focussed on users experiences with their scooters and gathered data only from users over 65. Users started using scooters to maintain their levels of mobility either as a result of losing physical capabilities or when they stopped driving. Users satisfaction with scooter comes from users enhanced mobility. Respondents felt that using a scooter meant they were able to travel to more destinations, achieve more daily tasks, maintain more independence and increase their sense of wellbeing.

Both these two studies provide insight into the experiences of scooter usage. May et al. is particularly useful in understanding the experiences of older users. Both studies show that users view their scooters as a very positive part of their lifestyle. The main negative aspects to their experience are from a lack of accessibility from the built environment. By using current scooter users the data gathered is likely to be positively skewed. For a more rounded understanding it would be illuminating to talk to people who potentially could use scooters but do not and people who have used scooters in the past but no longer do.

Negative views of devices stem from accessibility and from interaction with pedestrians (Brandt et al., 2004; Evans et al., 2007; Steyn and Chan, 2008; May et al., 2010). In a study of different mobility devices, dissatisfaction was recorded where users found their device limited where they could access (Evans et al., 2007). In their study of mobility scooter users and powered wheelchair users, Brandt et al. (2004 also noted that some users had encountered difficulties in carrying out their activities and that the older the users were the less they felt their device was suitable for the activities they wanted to complete. These findings are echoed by mobility scooter users who found that accessibility into buildings, along pavements and on sloped surfaces was limited (Barton et al., 2014; May et al., 2010; Edwards and McCluskey, 2010).

4.2.4. Activity

Common activities carried out using mobility scooters were: going for a ride, shopping, daytrips and social visits to family or friends. Scooter trips are typically made by users between three to five times per week and the most common activity to carry out using a scooter was shopping, followed by visiting local places.

Two studies found evidence suggesting that use of both powered wheelchairs and mobility scooters should be taken up earlier and be used by people who were less impaired than the study sample so as to delay activity dropout levels as a result of immobility (the Brandt et al. study covered mobility scooters and powered wheelchairs whereas May et al. study only looked at mobility scooters). This conclusion fits well with satisfaction literature, but its advice works against the literature on physical functioning and sedentary lifestyles.

4.3. Physical health

The bulk of the research in this area has been carried out on wheelchair users, their physical activity levels and their physical functionality and physical capabilities. This research is based on those who use their wheelchairs on a full time basis (generally Spinal Cord Injury patients, e.g. There are two reasons that these findings cannot be generalised to scooter users. Firstly, scooter users are able to walk, albeit often for only a limited distance. Secondly, manually propelled wheelchairs require physical effort to propel their chairs forward whereas scooter users do not. The research in this section is focused only on those studies that separately examine mobility scooters.

There are opposing views regarding the use of assistive technology which is physically passive and their impact upon physical functionality that can apply to mobility devices such as mobility scooters. On the one hand it is possible that mobility device use, including mobility scooter use, increases participation in both physical and social activities outside the home that users would have been unable to participate in without using such a mobility aid. Access to these activities, via mobility aid use, may increase aspects of quality of life and wellbeing in users. On the other hand assistive technology devices that are completely passive when the user does have some physical function, run the risk of de-conditioning the users physical functionality and their mobile capabilities at a faster rate than if they had used a more physically active assistive technology. It has been argued that scooters are a lifestyle choice rather than a medical necessity and therefore there is value in considering whether this lifestyle choice could be harming long term physical capabilities. Aside from theorising only two studies, have focused on objective functional physical health measures and mobility scooter use.

A study aimed to understand the effect of scooter use on the walking ability of people with knee osteoarthritis or rheumatoid arthritis. This randomised control study involved participants with either condition, who were able to walk 15 m independently. Participants were randomly either given scooters or maintained their usual care (control group). Participants walking abilities were tested, using a 6-min walk test, one month and three months after the scooter group began to use mobility scooters. Participants were questioned on the type of activities they participated in during the time period. The study found no significant differences in scooter users walking abilities when compared to the control group. However, scooters users were found to participate in a wider range of activities when they used the mobility scooters. The study concluded that, in terms of walking ability, mobility scooter use creates no adverse effects.

The randomised control methodology means the results will be accurate despite the small sample size (n=16). However, this study has a number of limitations. First, the study revisits the participants after 3 months and can only provide evidence for short term effects. This evidence cannot be used to understand or predict the effect over a longer period of time. It can be surmised that most scooter users will use their scooters for a longer time period than 3 months (Barton et al. found that most users have owned their scooters for at least two years) and this length of time might be too short to pick up evidence of a change in locomotory capabilities. It would have been more interesting had the group been studied over a longer period to determine the existence, timing, and persistence of any such change. Secondly, the study examines individuals with a specific condition known to affect mobility. From this viewpoint the study can make no comment on those who take up scooters for other reasons (for example as a result of pre-clinical disability). Thirdly, the scooter group were more likely to already be using wheelchairs at baseline. If these users are merely substituting time spent in the wheelchair with time spent in the scooter then no extra sedentary behaviour is occurring and therefore minimising the effects.

Zagol and Krasuski (2010) aimed to understand whether providing patients with mobility scooters increased their cardiovascular risk. The study was a retrospective analysis of data of patients from an army medical centre in the United States. Patients who had received a mobility scooter within a six-year period (1998–2004) were included and their medical data one-year prior and one year post receiving their scooter was extracted (n=102). Once selected, this group was sent a questionnaire on usage of the mobility scooter, as well as perceived wellbeing and quality of life post and prior to receiving a scooter.

From the data available, BMI, weight, cholesterol, blood pressure, fasting glucose level and medication was included. This enabled a cardiovascular risk to be created for each individual. Cardiovascular risk was measured for 12 months before a mobility scooter was prescribed, as a baseline, and 12 months after a mobility scooter was prescribed.

The study found a statistically significant increase in fasting glucose level (from 119–133 mg/dl), in haemoglobin Alc (6.3 to 6.8) and in the incidence of diabetes. BMI did not change and nor did systolic blood pressure. However, 20% of patients had their blood pressure medication increased or had additional blood pressure medication prescribed during this time. At odds with the medical data, the questionnaire data found that patients felt their mental wellbeing, their perceived physical functionality and their overall quality of life had improved between pre and post mobility scooter uptake. The results of this study provide some evidence that mobility scooter use may have negative impacts on physical functionality.

The study had a couple of limitations. Firstly, no control group was studied and it is therefore it is not known whether a similar population without scooters would have similar changes in cardiovascular risk. A matched control group from the same database would have shown whether or not this was the case. In response to this criticism from, Zagol and Krasuski stated that the incidence of diabetes in their sample was much higher than expected in an age-adjusted population (9.1 in 1000 individuals in the United States versus 301.6 per 1000 individuals in the sample). Secondly, as it is impossible to isolate all the overlaying factors the changes must be acknowledged as a correlation and causality cannot be assumed.

4. Policy

there has been some policy interest in mobility scooters. The governments focussed their attention on safety regulations and reports of accidents, noting anecdotal evidence of increases in numbers of users. It was recommended that any future legislations must carefully worded so not to deprive users of their only independent transport mode. The Department for Transport commissioned Ricability to carry out a study on the practices and policies related to scooter use on public transport. The study identified a lack of information about mobility scooter specifications and recommended that more information needed to be made available to allow transport operators to know which scooter types would fit on their vehicles and for users to know which operators allowed scooters on-board and what dimensions and permits were required.

5. Current and future research

There are many aspects of mobility scooter use that would be useful to explore. Given the evident upward trend of the use of mobility scooters this is crucial to understanding the role mobility scooters can play in individuals׳ lives. Currently the impact of mobility scooters on their users could be detrimental or beneficial in a variety of different ways. Could and should they be medically prescribed (they can be claimed on medical insurance in America but not )? Should they be guaranteed to be accommodated in public transport or in public buildings? Without a comprehensive body of research neither individual users, carers, health professionals or policy makers are able to make informed decisions on their use in a way that would be beneficial.

Older people are the group most likely to develop mobility difficulties and the most likely to start using a mobility scooter. Research, undertaken by the Accessibility Research Group at University College London is currently investigating the impact that mobility scooter use has on long term health in older people. This research is a longitudinal study using quantitative and qualitative data from mobility scooter users and non-mobility scooter users. Prior to mobility scooter uptake both groups had similar levels of physical capabilities. A scoping study using ELSA data of scooter users over 65years old has concluded that mobility scooters users perform worse at physical functioning tasks than other old people. Additionally, mobility scooter users have the highest rates of non-completion of physical tasks due to incapacity. The reasons behind the low scores and declines in capability are unclear and cannot be unearthed using the currently available data. However, scooter users poor record shown here indicates the need for it to be investigated, something which the follow up research will achieve. To balance the research on physical functionality further investigation into the psychological gains such as on independence and wellbeing is being undertaken. Results from these studies is expected in late 2015.

6. Conclusions

Research literature and empirical studies surrounding mobility scooters are sparse. In terms of user experience most users felt their scooter has had a positive impact upon their lives and perceive their scooter in a positive light. Their scooter meets their needs by enabling them to independently achieve their desired activities. It is clear that matching the mobility device to the individual and training the individual to use their mobility device is important. However, neither of these occur regularly.

The impacts of scooter usage on functional health is less clear. The relationships between frequency/length of use to physical functionality and capabilities has not been investigated. Where mobility scooter data does exist it is most often inseparable from wheelchair data, particularly electronic wheelchair data. Given the different physical capabilities of their users this is unhelpful. The two works that focus solely on mobility scooters and physical health impacts investigate different aspects of physical health (physical and functional), have different limitations and reach different conclusions.

Health research into mobility scooters is underexplored. Physical health literature is clear that a lack of physical exercise leads to a loss of functional capabilities including mobility in older adults. Also known is that the use of wheelchairs and scooters is increasing in the population despite no increases in levels of people with mobility difficulties. What is not clear is the role that mobility devices, particularly those where no physical effort is required, play. Whilst there is a wealth of data on the relationships between physical activity, health and ageing there is a lack of evidence on the role mobility devices play in promoting physical functioning and physical capabilities. The debate between mobility scooter users positive experiences and perceptions and the possibility that using scooters causes functional decline is of great interest and importance. As these topics have had such little quantification there is value in amassing evidence for both topics and how they interact. It is plausible that some scooter users sacrifice physical functioning for improved activity participation and independence. Empirical evidence showing the benefits and disadvantages of scooter usage is needed to allow those prescribing, recommending or choosing to use a scooter to make a fully informed choice.