Transport and Health

A policy report on the health benefits of increasing levels of cycling in Oxfordshire

(This was the basis for my dissertation for the MSc in Public Health at LSHTM back in 2000. It looks rather basic from where I sit now, but I've left it up here for old times' sake....)

Introduction

The increasing popularity of car travel over the last few decades has had major consequences for the lives of individuals, communities, society, and the environment. Cars have brought enormous freedom and opportunities for independence to many people, but the costs have been significant, and are disproportionately borne by the most disadvantaged groups in society. Aside from traffic deaths and injuries cars produce many other negative effects, such as noise and air pollution, and the social impacts of busy roads, such as community severance and social exclusion. Children's lives are now led very differently from the way they were a generation ago, with anxious parents shielding their children from what are perceived as the major hazards of dangerous roads and 'stranger danger'.1 Although cyclists often fear for their lives as they ride through traffic, the major health risks on the roads are in fact carried by sedentary drivers, who are more likely to die as a result of their particular lifestyle choice than any other group.

Levels of physical activity within the population are declining, and sedentary lifestyle is a major risk factor for coronary heart disease. Since Morris found that bus drivers suffer more heart attacks than bus conductors.2 the evidence has been mounting for the health benefits of physical activity; these are greatest when it is performed regularly over a lifetime. Regular cycling to work is an effective way of incorporating this exercise into daily routines; it can also have the beneficial effect of reducing traffic, a major disincentive to cycling, thus encouraging more people to use their bicycles for all sorts of travel.

his report has concentrated primarily on cycling because it is more likely to be an appropriate mode of transport for the kinds and lengths of journeys under consideration,3 but walking can be equally beneficial to health,4 and many of the same recommendations apply.

Aims

This report addresses the health costs of car and cycle transport, and the health risks of sedentary lifestyles. The aim of the report is to investigate aspects of the potential health benefits of achieving an increase in self-powered travel (walking and cycling) and a commensurate decrease in car use.

Having reviewed the evidence for the health benefits of exercise and the health costs of car use, and established the key local issues through discussion with stakeholders, a series of recommendations will be made for action by Oxfordshire Health Authority and other agencies.

Background

Public health importance

Health and transport are inextricably linked. Current levels of motorised transport have major consequences for public health, both in terms of the health impact of sedentary lifestyles, and the environmental and social effects of traffic.5 6 7

Policy context

The World Health Organisation Transport, Environment and Health programme has stated that 'sedentary lifestyle, one of the two most important risk factors for non-communicable disease and early mortality in Western populations is associated with the use of motor vehicles. There is a need to promote healthy and sustainable transport alternatives as a way to prevent the negative impacts of transport systems on human health. One important way to do this is to ensure that health issues are clearly on the agenda when transport decisions are being made and policies formulated. This requires…a change in the current strategies towards full consideration of transport policy implications for development, the environment, and health'.8

In the UK there have been many recent national and local policy initiatives encouraging exercise in general and cycling in particular. The National Cycling Strategy 9 was produced by the Conservative government in 1996, with targets to double cycling from 1996 levels by 2002, and quadruple them by 2012. The Department of the Environment, Transport and Regions' (DETR) Transport 2010: The 10 Year Plan 10 contains a commitment to providing safer cycling and walking routes, and more 20mph areas and Home Zones, particularly around schools. The Government's road safety strategy has set casualty reduction targets for 2010 of a 40% reduction in the number of people killed or seriously injured in road accidents, a 50% reduction in the number of children killed or seriously injured, and a 10% reduction in the slight casualty rate. It also acknowledges the importance of road safety for broader health, environmental and social inclusion issues.9

Several recent initiatives from central government are also highly relevant. Our Healthier Nation included a commitment to reduce the death rate from CHD, stroke and related diseases in people aged under 75 by at least 40% by 2010; it also set a target of reducing accidental deaths by 20% and serious injuries by 40%, and made a commitment to 'improve conditions and give greater priority to pedestrians and cyclists.'11 The Department of Health National Priorities Guidance 2000/01 - 20002/3 states that 'all health authorities [are] to develop and implement local prevention policies on CHD and stroke by March 2001'.12

The National Service Framework (NSF) for coronary heart disease, has among its targets a requirement that the NHS should 'develop, implement and monitor policies that reduce the prevalence of coronary risk factors in the population, and reduce inequalities in risks of developing heart disease.' It also states that by April 2001 'health authorities, local authorities, PCGs/PCTs, and NHS trusts will have agreed and be contributing to the delivery of the local programme of effective policies on…increasing physical activity' in order to reduce the incidence of CHD. The first of the four principles underpinning the NSF is that 'reducing the burden of CHD is not just the responsibility of the NHS. It requires action right across society'; it also states that 'publicly funded bodies will work together to tackle the broad determinants of health, including…transport. They will help children and adults have the opportunity to lead healthy lives, for example by increasing the opportunities for regular physical activity…'13

Current transport patterns are a major source of health inequalities. The Independent Inquiry into Inequalities in Health recommended 'further measures to encourage walking and cycling as forms of transport and to ensure the safe separation of pedestrians and cyclists from motor vehicles', and 'further steps to reduce the usage of motor vehicles to cut the mortality and morbidity associated with motor vehicle emissions', along with 'further measures to reduce traffic speed, by environmental design and modification of roads, lower speed limits in built up areas, and stricter enforcement of speed limits.'14

The foreword to the Oxfordshire Health Improvement Programme (HImP) for 2000-2003 identifies transport as one of the two key issues to be tackled. The programme supports the importance of physical activity in the prevention of CHD and diabetes, and contains local targets for reducing death and serious injury from accidents for both adults and children. It sets out several relevant objectives, such as those to promote healthy lifestyles to reduce the incidence of CHD and stroke, to develop transport policies that will benefit health, to reduce traffic and transport problems generated by the health care sector, and to improve local collection of accident data.15

Oxfordshire County Council produced cycling 16 and walking 17 strategies in 1999, along with a corporate travel plan.18 The cycling strategy contains a target to increase the proportion of cycle trips to work from 9.2% in 1991 to 10% in 2001, and 20% in 2011, and in 1993 Oxford City Council set itself a target to increase cycle use by 50% by 2001.

Current situation in Oxfordshire

Oxfordshire County Council is the highway authority for the county, although it has devolved certain powers, notably in the form of an agency agreement with Oxford City Council, which has responsibility for the majority of highways within its boundaries.

Oxford has in the last 18 months seen major changes to its traffic system as a result of the Oxford Transport Strategy (OTS); these have generated significant controversy. The strategy was first conceived by the City and County councils in the 1970s as a response to the increasing traffic flows within the city, and developed over the subsequent two decades with the aim of maintaining traffic levels at those at the time of its inception. The first phase of the OTS was implemented on 1 June 1999 with the closure of the High Street to through traffic and the pedestrianisation of Cornmarket, a major central shopping street which until that time had been a major bus thoroughfare.

Methods

The formal development of this report was conducted in three main parts: an analysis of local and national data on transport and health, a review of the evidence for the health benefits of exercise, and interviews with local stakeholders and other experts concerned with cycling and other local transport issues.

Travel, injury, and other data

Statistical and other data were obtained from appropriate sources, including the Office for National Statistics (ONS) and the DETR. The Information Team at Oxfordshire Health Authority was exceptionally helpful, and provided a wide range of these data in the appropriate formats.

Literature review

Major electronic databases were searched for relevant papers. The search terms were selected to emphasise sensitivity rather than specificity. Results were closely inspected for relevant papers, which were then selected on the basis of quality criteria.19 Other studies were located by studying citations within the papers obtained, and from previous work in this field. The staff of the Institute of Health Sciences library were extremely helpful, both in providing advice and training on search strategies, and in obtaining references.

Other sources of information included literature and references obtained at two conferences on cycling and health, one organised by the British Medical Association, the other by the Road Danger Reduction Forum. As a co-opted member of both the Highways and Traffic Committee and the Pedestrians' and Cyclists' Sub-Committee of Oxford City Council, I was able to observe discussions and decisions concerning local cycling and other transport issues. Academics and other experts were contacted for suggestions of key documents, and interviewees were extremely helpful in suggesting and providing sources of important information.

Stakeholder views

Local stakeholders were identified in a number of ways. Previous work on cycling for Oxfordshire Health Authority had involved contact with relevant local people, who were also able to suggest other suitable contacts. It was felt important to obtain a broad spectrum of political views from within local government, as well as contributions from the police, the universities, bus companies, representatives of local businesses, Oxfordshire Health Promotion, health service staff, and others. Mayer Hillman, Senior Fellow Emeritus at the Policy Studies Institute, a transport and health policy expert and the author of the original BMA book 20 which inspired this report, was also interviewed as an expert in the field.

The purpose of the interviews was to obtain information about local issues relevant for cycling, such as major political and community concerns, the viewpoints of the people involved in making the decisions, and obstacles to development within the current structures. It was also hoped that some unanticipated insights, and potential solutions to some of the problems, would become apparent.

Interviews were conducted either in person or by telephone, apart from one interviewee who gave a written response to the questions and requested anonymity; everyone approached for interview agreed to participate. Most interviews took around 30 minutes, although some lasted well over an hour. All interviewees will be sent a copy of this report.

Interviews were preceded with an explanation of my role and the purpose of the report. The interviews were semi-structured around a small number of questions. Discussion beyond the terms of the questions was encouraged. Notes were taken during the interview, typed up afterwards, and analysed in several stages. Major themes were identified and analysed in terms of factors such as the respondent's cycling experience and rural or urban location.

Results

Travel, injury and other data

The most recent year with full mortality, population, and transport data available is 1998; other years have been selected where they were the most recent quoted in reliable sources. The current Department of Transport (now DETR) report on Cycling in Great Britain, for example, was published in 1996.

Cycling and travel

38% of households overall, and 69% of those with two or more children, own at least one bicycle. Cycle ownership is linked to household income: about a quarter of households in the lowest 40% of incomes own a cycle, compared to nearly half in the remaining 60%.9

Bicycle usage has declined from 23.6 billion vehicle kilometres in 1949 to 4.0 billion in 1998; car use has increased from 20.3 billion vehicle kilometres to 375.9 billion in the same period.21 As a proportion of all road traffic, cycling has declined from 37% in 1949 to less than 1% in 1998; cycling accounts for 3.4% of journeys to work in England, but only 1.5% in Wales and Scotland.22 About a quarter of journeys travelled by bicycle are less than a mile, and another third between one and two miles; a quarter of car journeys are less than two miles.9

With 17.4% of residents cycling to work in 1991, Oxford has the third highest levels of cycle usage in the country, after Cambridge at 28.2% and York with 19.0%.9 The biannual census of pedestrian and vehicle flows into Oxford shows that the number of cyclists entering the city has increased slightly between 1996 and 2000, but remains steady around 15,500 per day. However, as the number of cars entering the census cordon points has decreased, the number of cycles as a proportion of total vehicles has increased from about 16% in 1996 to about 20% in 2000.23

A 1996 study of two Oxfordshire villages found a median car journey length of half a mile for people aged 30-59 travelling within their village; 25% of all journeys were four miles or less. It would have taken 25 minutes or less to walk (i.e. 10 minutes or less to cycle) rather than use the car for 40% of the journeys to work. The report states that 'for work journeys, the dominance of the car and acceptability of cycling to an office was explained in terms that indicated they were perceived as unalterable'; cars 'were recognised to marginalize other transport modes such as cycling and walking', and 66% of men and 71% of women supported reducing car use 'because of the associated health problems.' The study also found that the most affluent respondents had the highest levels of car ownership and car usage; the 10% of households using the most energy for travel was the most affluent group, and travelled ten times further than the 10% of households using the least energy, which was the poorest group.24

Casualty rates

3,421 people died on Great Britain's roads in 1998, and 322,000 were injured. National cyclist death rates have declined from 842 in 1949 to 158 in 1998; this is in the context of a large decrease in bicycle usage, and reflects an increase in the numbers of cyclists killed per distance travelled of about 10%. Cyclists make up 7.3% of road casualties in the UK, but cycling is, in absolute terms, a low risk activity; there is one cyclist death per 21 million kilometres cycled.21 Men average more than three times the annual cycle mileage of women, and male casualties outnumber female casualties by four to one overall and five to one for those aged under 20.22 A 1999 study of child pedestrian injuries in Britain, France and the Netherlands found that the injury risk on Britain's roads, matched for equivalent exposure, is significantly greater than in the other two countries.25

The numbers of cyclists killed on the roads in Oxfordshire are too small to discern trends, but ranged from one to five, with a mean of two, between 1994 and 1998. Despite the small numbers a standardised mortality ratio (SMR) for cycling deaths in Oxfordshire between 1994 and 1998 was calculated with a result of 131 (95% CI: 45-194). With cycle commuting rates in the county over five times the national average, and presumably other usage rates to match, even the upper limit of the 95% confidence interval for the SMR is less than half what one would anticipate given this level of cycling, suggesting that Oxfordshire is a relatively safe place to cycle.

Life years lost

Table 1 shows the numbers of life years lost through cyclist deaths in Oxfordshire 1994-98. The large year-to-year variation is a result of the inevitable random variations with small numbers of people of different ages dying. Life expectancies were calculated for each of the years 1994-98 from ONS population and mortality figures using standard formulae,26 and life years lost were then calculated by multiplying the number of deaths within each five-year age band by the life expectancy for that age band. The same calculations were also performed for CHD deaths both nationally and locally.

Table 1: Life years lost from cycling deaths and coronary heart disease deaths 1994-98

	1994	1995	1996	1997	1998	5 year total
Life years lost: cycling deaths
England & Wales	3,969	5,859	7,051	6,330	6,599	29,808
Oxfordshire	106	31	27	23	167	354
Life years lost: coronary heart disease deaths
England & Wales	1,561,552	1,502,686	1,465,933	1,396,028	1,417,452	7,343,651
Oxfordshire	12,621	11,529	12,387	11,849	12,279	60,665

Activity levels

The 1998 Health Survey for England found that 63% of men and 75% of women exercise less than 30 minutes on most days; 20% of men and 24% of women reported less than 15 minutes of physical activity in the previous four weeks.27 A local survey of 2,056 people in 1997 found that 13% exercise three or more times a week, but 46% exercise less than once a month. Those in social class V are more than twice as likely to be sedentary as those in social class 1, and those in social class 1 are over three times as likely to exercise three or more times a week as those in social class V.28

Literature review

General points

There is a large body of evidence for the beneficial health effects of exercise on mortality and morbidity, especially from cardiovascular disease. Although different studies have taken a number of approaches to assessing and classifying activity levels, making comparison between studies difficult, it is nevertheless possible to draw broad conclusions about the activity levels required to benefit health.

Physical activity and mortality

A major review article in 1995 stated that approximately 12% of deaths in the United States are attributable to lack of physical activity, and concluded that every adult should engage in at least 30 minutes of moderate exercise on most, preferably all, days of the week. It defined moderate activity as that which expends 4-7 kcal/minute, such as brisk walking, or cycling for leisure or transport.29 A review that categorised the population as sedentary, irregularly active, regularly active, or vigorously active found that the greatest health benefits would accrue from increasing the exercise levels of the irregularly active group.30 A meta-analysis of physical activity in the prevention of CHD supported a dose-response relationship between exercise and protection from CHD.31

A prospective study of over 13,000 men and women found that those in the least fit quintile had relative risks of all-cause mortality of 1.58 (95% CI: 1.32, 1.89) for men, and 1.94 (95% CI: 1.30, 2.88) for women, compared with those in the most fit quintile, with a strong and graded association between physical fitness and mortality.32 In a study of 10,269 Harvard alumni those who were previously sedentary but took up moderate physical activity during the course of the study had a 41% lower risk of death from CHD than those who remained sedentary, and added 0.72 years of life (95% CI:0.14, 1.29).33 An earlier study of 16,936 Harvard alumni found that those expending less than 2000 kcal/week had a relative risk of fatal heart attack of 2.01 compared to those expending over 2000 kcal/week (p=0.001).34 A follow-up to this study found that death rates declined steadily as energy expenditure increased from below 500 kcal/week to 3500 kcal/week, with rates 25-33% lower in those expending over 2000 kcal/week compared to those expending less than this. By the age of 80 the amount of additional life attributable to adequate regular exercise, as opposed to sedentary lifestyle, ranged from one to over two years.35 There has until recently been a dearth of good evidence for the benefits of activity in women, but this situation has now been redressed with several large, high-quality studies showing equivalent benefits to those found in men.36 37 38

Physical activity and morbidity

In addition to the effects on cardiovascular morbidity discussed above, regular exercise has been shown to be beneficial in many conditions4 including diabetes 39 40 and insulin sensitivity,41 42 hypertension,43 44 stroke,45 elevated blood lipids,46 47 obesity,42 and cancer.48

There is evidence to support a relationship between physical activity and psychological well-being 49 50 and a recent review shows that low to moderate physical activity has beneficial effects on depression, stress,51 mood, self-esteem and premenstrual syndrome.52 Physical activity has been shown to improve cognitive function in the elderly,53 and reduce falls.54 Regular exercise allows elderly people to maintain a reasonable degree of fitness for activities of daily living,55 and a review of the relationship between physical activity and hip fractures found a protective effect of the order of a 50% reduction in the more physically active subjects.56

Stakeholder views

Interviewees live across the county, some in urban and some in rural areas, although the majority of them live in or near Oxford. Only one respondent does not cycle at all, and about half cycle regularly.

Those who lived in urban areas were more likely to cycle further and more frequently than those in rural areas, with long distances and high speed traffic on narrow roads cited by the latter group as disincentives. Experienced and higher mileage cyclists were more likely to cycle on the carriageway, and were less likely to be put off cycling by bad weather, traffic or other factors.

Fear of traffic danger was overwhelmingly the greatest disincentive to cycling. Segregation from vehicles, lower traffic speeds, and continuous cycle lanes were felt to be the most important mechanisms to counter the threat of traffic. There was broad agreement on this from the majority of respondents, with less experienced cyclists especially keen. Large vehicles, especially buses, were felt to be the most threatening.

The interviewees were broadly supportive of the projects and facilities currently in place for cyclists, and there was general agreement that they should be taken further; discontinuities in cycle lanes in particular were seen as a problem, especially by less experienced cyclists. Bicycle theft is a major concern, and greater provision of secure cycle parking was felt to be essential.

Many of the interviewees felt that employers should provide facilities such as secure cycle parking, lockers, and showers at work. There was also support for financial incentives, such as subsidies for cycle and equipment purchase, and generous mileage allowances. There was widespread criticism of the health sector for apparently failing to get its own house in order, and not leading the way with its own staff.

Several respondents stated that a process of cultural change was required to encourage more people to cycle, especially in relation to their employment. It was felt that while certain workplaces were very supportive of cycling, in others where it was not culturally accepted there would be greater obstacles to those who did want to cycle. The need to look smart at work was cited several times as a reason for people not to cycle, including by regular cyclists, as were difficulties carrying bulky items.

There was strong support for effective joint working, and public consultation, but problems were identified with both these activities. While members of all agencies were keen to work closely with their counterparts elsewhere, many respondents felt that current arrangements were ineffective, and the City Council / County Council split in Oxford was felt to be a particular barrier. Many reasons were cited for these problems, including a lack of appreciation of one another's perspectives, differing agendas, and budgetary constraints. There is little money available for public consultation, which is expensive and time consuming, and several interviewees reported practical difficulties in obtaining the views of the general public.

Many other points were raised, including:

• Widespread criticism of poor and/or illegal behaviour by cyclists

• Local Authorities across the country have a standardised system for collecting transport and accident data, allowing comparison between authorities; no such system exists for health data

• It is important to recognise the different needs of town and country dwellers. In rural areas roads tend to be narrower with higher speed traffic, and journeys made over greater distances. As a result safe, comfortable off-road routes, as have been created by Sustrans for the National Cycle Network,57 were felt to be necessary outside the major towns

• The Oxford City cycling map was very popular, and felt to be an excellent encouragement to leisure cycling

Discussion

Health benefits of exercise

Paffenbarger et al's Harvard alumni study of 1986 35 provides useful data for plotting the relationship between exercise and mortality. It includes a table relating activity levels (as defined by energy expenditure) to risk of all-cause mortality; a simple calculation allows energy expenditure to be expressed as time spent cycling, and a graph of relative risk against cycling time can then be plotted (Figure 1). The reason for the increased mortality above 3500 kcal/week is not clear, and is at odds with other studies which have shown similar gradients for reduction in mortality from increasing activity at much higher levels of energy expenditure.58

Deaths from all causes in Oxfordshire in the years 1994-98 led to a loss of 340,343 life years. Relating this to the health benefits of exercise shown in Paffenbarger's study 35 allows an estimate of the number of life years that could be gained as a result of deaths avoided if cycling activity were to increase, as shown in Table 2. A relative risk of 0.78 was used for the calculations as this is the appropriate relative risk for people exercising at a level equivalent to cycling for 20-40 minutes/day at 10mph. This reflects the potential benefit available even to inexperienced cyclists making short journeys. If 1% of the population took up cycling these people would reduce their risk of all cause mortality by (1.0-0.78) - i.e. by 22%. These calculations are inevitably crude, but they give a rough idea of the order of magnitude of the potential benefits. The calculations are based on an assumption that cycling deaths increase linearly with increasing levels of cycling. It appears, however, that cycling becomes safer as cycling levels increase (see section on Speed and Danger below). I have also assumed that the risk exposure within this sub-population is the same as that within the general population. I have requested more detailed figures on this risk exposure from the DETR, and will update the calculations once I have received them.

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