Health effects of the London bicycle sharing system: health impact modelling study

Abstract

Objective To model the impacts of the bicycle sharing system in London on the health of its users.Design Health impact modelling and evaluation, using a stochastic simulation model.Setting Central and inner London, England.Data sources Total population operational registration and usage data for the London cycle hire scheme (collected April 2011-March 2012), surveys of cycle hire users (collected 2011), and London data on travel, physical activity, road traffic collisions, and particulate air pollution (PM2.5, (collected 2005-12).Participants 578 607 users of the London cycle hire scheme, aged 14 years and over, with an estimated 78% of travel time accounted for by users younger than 45 years. Main outcome measures Change in lifelong disability adjusted life years (DALYs) based on one year impacts on incidence of disease and injury, modelled through medium term changes in physical activity, road traffic injuries, and exposure to air pollution.Results Over the year examined the users made 7.4 million cycle hire trips (estimated 71% of cycling time by men). These trips would mostly otherwise have been made on foot (31%) or by public transport (47%). To date there has been a trend towards fewer fatalities and injuries than expected on cycle hire bicycles. Using these observed injury rates, the population benefits from the cycle hire scheme substantially outweighed harms (net change −72 DALYs (95% credible interval −110 to −43) among men using cycle hire per accounting year; −15 (−42 to −6) among women; note that negative DALYs represent a health benefit). When we modelled cycle hire injury rates as being equal to background rates for all cycling in central London, these benefits were smaller and there was no evidence of a benefit among women (change −49 DALYs (−88 to −17) among men; −1 DALY (−27 to 12) among women). This sex difference largely reflected higher road collision fatality rates for female cyclists. At older ages the modelled benefits of cycling were much larger than the harms. Using background injury rates in the youngest age group (15 to 29 years), the medium term benefits and harms were both comparatively small and potentially negative.Conclusion London’s bicycle sharing system has positive health impacts overall, but these benefits are clearer for men than for women and for older users than for younger users. The potential benefits of cycling may not currently apply to all groups in all settings.

Air pollution as a risk factor in health impact assessments of a travel mode shift towards cycling

“…In one study, Johansson et al [37], individual data on people’s home and work addresses were used, as well as their age, sex, and expected physical capacity, in order to establish realistic bicycle travel distances. Rojas-Rueda et al [38] and Woodcock et al [39] evaluated the current benefit of increased cycling due to a public bicycle-sharing program. Dhondt et al [40] simulated the travel activity patterns before and after an increase in fuel prices, while Macmillan et al [41] simulated the effects of policy changes employing the System Dynamics Modelling.…”

“…The health impacts of increased physical activity resulting from increased cycling were evaluated in all studies. Physical activity was mainly reported as distance or time spent in active travel, except in seven studies – Dhondt et al [40], Maizlish et al [34], Woodcock et al [35,36,39], Buekers et al [47] and Rojas-Rueda et al [43] – where it was expressed as metabolic equivalent of task (MET) hours per week. All except two studies – Holm et al [42] and Xia et al [46] – measured physical activity as a continuous variable and employed published risk estimates to evaluate the health impacts of increased cycling.…”

“…Nine studies examined the air pollution impact on the general population [34–37,40,41,46,48,50], four estimated impacts on active commuters [38,39,42,43], and five included impacts on both the general population and active commuters [22,44,45,47,49]. The included studies modeled both particulate and gaseous pollutants such as particulate matter (PM) less than 2.5 µm and less than 10 µm (PM2.5 and PM10), sulfur dioxide, nitrogen dioxide (NO 2) and nitrogen oxides (NOx), carbon monoxide, ammonia, etc.…”

“…Among the studies including morbidity and mortality outcomes that quantified BoD, the Disability adjusted Life Years (DALYs) was estimated by calculating YLD and YLL [34–36,39,40,42,45,46]. Some studies also performed sensitivity analyses to tackle uncertainties associated with the use of published RRs.…”

“…All nine HIA studies in our review that estimated the active commuters’ exposure to air pollution did this on the basis of the pollutant concentration in the ambient air, the trip duration, and the ventilation rate during cycling [22,38,39,42–45,47,49]. The basic differences between studies are in the way they calculated pollutant concentrations in traffic and what ventilation rate they assumed.…”