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The health risks and benefits of cycling in urban environments compared with car use: health impact assessment study

BMJ 2011; 343 doi: (Published 04 August 2011) Cite this as: BMJ 2011;343:d4521

Rapid Response:

Authors' reply for Dr Fishman and Dr Soutter

Evaluating the benefits of public bicycle schemes needs to be
undertaken carefully: Response from the authors.

We set out to estimate the health impacts of the Bicing system and
started with the assumption that 90% of the Bicing users previously made
the same trip by car, and conducted further (sensitivity) analyses using
other scenarios of mode shift (assuming that 9.6% of Bicing users came
from cars, 55.1% from public transport and 26.1% from walking) (1) (see
web appendix). As mentioned in the paper, they made little difference to
the results (10.46 vs 12.46 deaths avoided for the main driver of the
analyses physical activity), thus not changing the main message of the
paper. In our analyses we found that there may be greater benefits from
walking compared to cycling, and reported an increase of 0.61 deaths in
the Bicing population from those who previously walked for 2km on a
regular basis and shifted to Bicing for the same amount of travel.

Traffic incidents mortality: author's response

We found that the difference in traffic incidents between cyclists
and car drivers was less than reported in UK(2), possibly because we did
the calculation of risk for an urban area and not the whole country
(resulting in less miles travelled and fewer deaths). Cycling mortality
reported in Barcelona (and used in this study) was very low (5 deaths in
the last 9 years) resulting in a low comparative risk between cycling and
driving. We conducted sensitivity analyses using the higher traffic
mortality rates reported by De Hartog(3) and found little impact on our
final results.

Table. Traffic fatalities rate in bike and car (deaths per billion kilometres travelled).

Reference List

1. Rojas-Rueda D, de Nazelle A, Tainio M, Nieuwenhuijsen MJ. The
health risks and benefits of cycling in urban environments compared with
car use: health impact assessment study. BMJ 2011;343:d4521.

2. Department for Transport. Reported Road Casualties Great Britain
2009. 2010. London, UK, Transport Statistics Publications.

3. De Hartog JJ, Boogaard H, Nijland H, Hoek G. Do the health
benefits of cycling outweigh the risks? Environ.Health Perspect.

Competing interests: No competing interests

09 September 2011
David Rojas-Rueda
predoctoral researcher
Audrey de Nazelle researcher and Mark J Nieuwenhuijsen research professor
Center for Research in Environmental Epidemiology, Barcelona, Spain