Encouraging cycling is a good thing, argue docs19/10/2010 Bike to Work
But exactly what works best and whether the efforts are worth it is harder to measure, says a new study in the British Medical Journal
Medical statisticians at Cambridge’s Clinical Research Collaboration Centre for Diet and Activity Research (CEDAR) have number-crunched 25 cycling and active travel schemes from seven countries. Disparity in measurement criteria and other downers led the paper authors to conclude that, while cycling has clear health benefits, it’s far less clear how to get people on bikes in the first place.
The CEDAR study, led by Dr David Ogilvie, was set up to find out “what interventions are effective in promoting cycling, the size of the effects of interventions, and evidence of any associated benefits on overall physical activity.”
After analysing the 25 studies, Dr Ogilvie and his team found that promotional activities and improving infrastructure for cycling have the potential to increase cycling by only “modest amounts.”
The CEDAR team want to see more “robust study designs” so that cycling’s health benefits can be rolled out to more people.
And, CEDAR concludes: “Cycling offers a highly efficient substitute for short car trips of up to several miles. As such, promoting cycling could also help to reduce traffic congestion, air pollution, and carbon emissions.”
Studies evaluated included the BikeTexas Safe Routes to School intervention; cycle path connectivity in the Dutch city of Delft; the Danish National Cycle City project which included promotional campaigns and infrastructural measures; and Cycling England’s Cycle Demonstration Towns, created in 2005.
“Most studies…did not report the statistical significance of any net increases in cycling,” found CEDAR.
“Furthermore, in most studies it is unclear whether such increases reflect new trips by infrequent or novice cyclists (which could represent early evidence of potential public health benefits) or additional trips by existing cyclists (which are less likely to contribute significant public health benefits).”
Dr Ogilvie concluded that “significant reservations remain about…sources of bias or confounding in most studies, and, therefore, in the interpretation of their results. These reservations include the reliance of many studies on self reported measures of cycling that are widely accepted but are of unknown validity and reliability.
“Although the evidence does suggest that a variety of approaches have clear potential to promote cycling, from a population perspective, the effect sizes attributable to the interventions studied to date appear relatively modest.”
But this shouldn’t mean such interventions shouldn’t take place:
“There is nevertheless a strong case for promoting cycling on health grounds. At the individual level, cycling to work or school has been shown to be associated with greater cardiorespiratory fitness in adults and children, respectively, and in the Copenhagen City Heart Study cycling to work was associated with a significant reduction in mortality even after adjustment for leisure time physical activity…Two recent studies modelling the health effects of a population shift towards active travel have independently concluded that the health benefits attributable to greater use of physically active modes of transport substantially outweigh any adverse effects related to risk of injury or exposure to inhaled pollutants.
“Promoting cycling is, therefore, a viable approach to improving health.”
The CEDAR team, while based in cycle-friendly Cambridge, with its myriad of bike paths, say studies can’t confirm that the segregation of cyclists from motorised traffic has as big a benefit as many like to claim:
“Evidence from observational studies suggests that changing the built environment has the potential to influence cycling behaviour, but few data from controlled intervention studies are currently available to confirm this. Our review shows that it is unclear whether increases in cycling could be achieved at lower cost by addressing attitudes and perceptions about cycling.”
According to research by Cycling England, the UK’s six Cycle Demonstration Towns saw a 25 prevent increase in the number of trips taken by bike between 2005 and 2009.
In 2005, six places were chosen to be Cycling Demonstration Towns – Aylesbury, Brighton and Hove, Darlington, Derby, Exeter and Lancaster with Morecambe. Bristol was later added as a Cycling Demonstration City.
The Department for Transport provided each town with £5 per head to spend per year, match-funded by local authorities. The average amount spent by other local authorities on cycling has usually been £1 per head.
Aylesbury used the funding to publicise its existing cycle routes with colour coding and signs. Darlington doubled the length of its cycle path network. Brighton and Hove targeted neighbourhoods with personalised travel plans. Lancaster with Morecambe upgraded canal path routes.
Using automatic counters on selected routes, Cycling England said the first three years of the Cycling Demonstration Towns saw the number of trips taken by cyclists in the towns rising by an average of 27 percent.
Phillip Darnton, chairman of Cycling England, has ling maintained that: “The high levels of cycling in many European cities are the result of consistent policy and sustained investment over two decades. If the level of growth seen across the six towns is sustained for 20 years, cycling trips will rise fivefold. This will have a transformational effect on health and make a major contribution to cutting carbon emissions and congestion.”
Funding for the Cycling Demonstration Towns runs out in 2011. Last week, the Coalition Government abolished Cycling England.