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SHOR T PAPE R Open Access
Assessing the impact of road traffic on cycling
for leisure and cycling to work
Charlie E Foster
1*
, Jenna R Panter
2
and Nicholas J Wareham
2
Abstract
Background: To explore the relationship between leisure and commuter cycling with objectively measured levels
of road traffic and whether any relationship was affected by traffic levels directly outside of home or in local
neighbourhood.
Findings: We conducted a secondary analysis of data from the UK European Prospective Investigation of Cancer
(EPIC) Norfolk cohort in 2009. We used a geographical information system (GIS) and gender specific multivariate
models to relate 13 927 participants’reported levels of cycling with an index of road traffic volume (Road Traffic
Volume Index Score - RTVIS). RTVIS were calculated around each participants home, using four distance based
buffers, (0.5 km, 1 km, 2 km and 3.2 km). Models were adjusted for age, social status, education, car access and
deprivation. Both genders had similar decreases in leisure cycling as traffic volumes increased at greater distances
from home (OR 0.42, (95% CI 0.32-0.52, p < 0.001) for women and OR 0.41, (95% CI 0.33-0.50, p < 0.001) for men in
the highest quartile at 3.2 km). There was no effect of traffic volumes at any distance on commuter cycling.
Conclusions: Traffic volumes appear to have greater impact on leisure cycling than commuter cycling. Future
research should investigate the importance of traffic on different types of cycling and include psychosocial
correlates.
Keywords: Cycling, traffic, GIS
Background
Cycling is considered to be a healthy, low carbon and
sustainable physical activity behaviour [1]. Although
travel by bicycle does introduce health risks through
accidents and injuries [2] the health benefits of cycling
have been shown to outweigh these risks [3]. More
specifically, studies have suggested that commuter
cyclists have a lower mortality risk than non-cycling
commuters, independent of physical activity levels [4].
Across many international countries the numbers of
car trips are increasing and in some there are simulta-
neous declines in active travel trips by walking or
cycling [5].
Characteristics of the built environment are also sus-
pected to contribute to levels of walking and cycling [6],
although for active travel behaviors in particular the
evidence is inconsistent [7]. It could be hypothesized that
in areas which have both unsupportive built environments
for active travel and high traffic volumes, a double burden
of negative associations for active travel could be pro-
duced. International studies have focused on the negative
impact of perceptions of traffic levels and safety on walk-
ing and cycling but have not used objective measures of
traffic volume [8,9].
In our previous study, exposure to higher levels of
traffic around the home was associated with less leisure
cycling [10]. The aim of this study was to (i) explore the
relationship between leisure cycling and commuter
cycling with objectively measured levels of road traffic
derived using a geographical information system (GIS)
and (ii) investigate if any relationship was affected by
trafficlevelsdirectlyoutsideofthehomeorbetween
home and local destinations.
Methods
The UK EPIC-Norfolk study was designed as a prospec-
tive cohort study and the methods of recruitment, sam-
pling and overall sample representativeness have been
* Correspondence: charlie.foster@dphpc.ox.ac.uk
1
Department of Public Health, University of Oxford, UK
Full list of author information is available at the end of the article
Foster et al.International Journal of Behavioral Nutrition and Physical Activity 2011, 8:61
http://www.ijbnpa.org/content/8/1/61
© 2011 Foster et al; li censee BioMed Central Ltd. This is an Open Access article distributed under the terms of th e Creative Commons
Attribution License (http://creative commons.org/licenses/by/2.0), which permits unrestricted use, distribu tion, and reproduction in
any medium, pro vided the original work is properly cited.
described elsewhere [11]. Data on self-reported measures
of physical activity was collected from 15,786 adults
using EPAQ2 between 1998 and 2000. This questionnaire
asks about the frequency and duration of physical activity
at home, at work (including travel to work) and for
recreation, over the past 12 months. Ethical approval for
the EPIC-Norfolk study was given by the Norfolk
Research Ethics Committee.
Participants were asked to report how often they used a
bicycle to get to work using the response categories of
‘always’,‘usually’, occasionally’and ‘never or rarely’. Parti-
cipants were classified as commuter cycling if they
reported ‘always’travelling to work by bicycle. Leisure
cycling was assessed by three items which asked about the
number of occasions of cycling for pleasure, for racing and
rough terrain cycling. If participants reported at least 1
occasion of any of these activities they were classified as
engaging in ‘some’leisure cycling.
Objectivemeasuresofroadtrafficvolumewereesti-
mated using a GIS (ESRI ArcGIS 9.2). We calculated a
proxymeasureoftrafficvolume(RoadTrafficVolume
Index Score - RTVIS) for each participant using four
different distance based buffers around each indivi-
duals home postcode (0.5 km, 1 km, 2 km, 3.2 km). It
was calculated by computing the total lengths of four
different types of road (principal roads or motorways,
A-roads (major roads), B-roads (minor or local roads)
and unclassified roads) within these buffers (centred
on participants’homes) and weighting these based on
the average road speed for each classification [12].
Scores were divided into quartiles and the lowest quar-
tile was used as the reference group. Using a variety of
distance buffers allowed us to examine any potential
differences in the associations between cycling beha-
viourandtrafficvolumeatdifferent proximities, as
there is currently uncertainty about size of the area
from home which influences commuting or leisure
related activities. The choice of the largest radius size
reflected the UK government’s aim to encourage a
shift from car use to walking or cycling for short jour-
neys under 2 miles (3.2 km) [13]. We estimated that a
2 mile cycle journey (at 8 mph) should take an adult
approximately 15 minutes.
Possible confounders included age, gender, social sta-
tus, educational qualifications, area socioeconomic
deprivation, car ownership, ethnicity, and self-reported
health conditions.
We built a series of gender specific multivariate mod-
els to calculate the odds ratios of commuter and leisure
cycling associated with RTVIS adjusted for identified
confounders. We checked for effect modification and
interactions between variables at each stage of the
model [14].
Results
Physical activity data were available for 15 572 partici-
pants, however we excluded those who had incomplete
postcode data or had moved out of the study area
(5.9%), unusually high levels of self reported physical
activity (1.5%) and missing socio-demographic data
(3.1%). This left 13 927 participants for analysis.
Table 1 shows the characteristics of the sample.
A higher proportion of men reported any leisure cycling
compared to women, however we found a slightly
higher proportion of women reported any occasions of
commuter cycling than men (p < 0.05).
Table 2 presents the adjusted odds ratios for reporting
leisure and commuter cycling.
Using a 500 m buffer, an increasing RTVIS was asso-
ciated with higher odds of leisure cycling and women’s
commuter cycling. Yet, with larger buffer sizes the odds
of leisure cycling decreased with increasing RTVIS,
however there were no such associations observed for
commuter cycling for either genders.
Conclusions
Exposure to increasing level of traffic around home was
associated with a reduction in leisure cycling and not
for commuter cycling. Both genders had similar
decreases in leisure cycling as traffic volumes increased
between 500 m to 1000 m from home.
A few studies have reported conflicting associations
between characteristics of the built environment, traffic
and different types of cycling behaviour [8,15,16]. How-
ever direct comparison is difficult due to differences in
methods in construction of the outcome variable by
combining walking and cycling, or all cycling or cycle
path use. One case study of non-cyclists reported similar
impacts of traffic made cycling dangerous based on a
combination of the poor quality of the road environ-
ment, plus heavy and speeding traffic, and worries about
the dangers of cycling [17].
Triano and Freedson recently identified that a diver-
sity of non-comparable methods are a limitation to
environmental/behavioral research [18]. This study was
limited by use of a non-objective physical activity mea-
sure however data were collected before the possible
application of such measures could be realistically used
in such a large sample. Outcome variable data were col-
lected using appropriate methods for a large cohort
study, using a reliable and valid measure. The GIS
derived exposure measure is based on road transport
network and local road speed, which could easily be
adopted by other researchers to make cross-study and
country comparisons possible. The use of increasing
buffer areas for traffic also avoided any potential inter-
individual variation in the size of neighbourhood and
Foster et al.International Journal of Behavioral Nutrition and Physical Activity 2011, 8:61
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Table 1 Characteristics of participants by socio-demographic, physical activity and environmental variables
Men (n = 6134) Women (n = 7793)
Occasions of leisure cycling Occasions of commuter cycling Occasions of leisure cycling Occasions of commuter cycling
None Any None Any None Any None Any
Percentage of Subjects 80.1 19.9 96.2 3.8 85.1 14.9 95.7 4.3
Age
41-50 years of age 63.9 36.1* 91.4 8.6* 70.1 29.9* 91.5 8.5*
51- 60 years of age 73.0 27.0 93.4 6.6 80.4 19.6 93.2 6.8
61-70 years of age 82.7 17.3 97.6 2.4 893. 10.7 97.9 2.1
71-80 years of age 91.6 8.4 99.5 0.5 95.5 4.5 99.4 0.6
Social status
Professional 75.4 24.6* 95.0 5.0* 82.8 17.2* 95.2 4.8*
Managerial & Tech. 80.0 20.0 97.7 2.3 84.0 16.0 97.0 3.0
Skilled non-manual 80.6 19.4 97.1 2.9 88.9 11.1 97.3 2.7
Skilled manual 80.1 19.9 95.1 4.9 83.9 16.1 94.9 5.1
Partly skilled 82.2 17.8 93.3 6.7 85.5 14.5 92.4 7.6
Unskilled 85.1 14.9 94.2 5.8 84.2 15.8 91.0 9.0
Educational qualifications
Degree or higher 76.1 23.9* 95.9 4.1 80.4 19.6* 95.3 4.7
Any qualifications 78.9 21.1 96.4 3.6 83.3 16.7 96.3 3.7
No qualifications 85.0 15.0 95.7 4.3 88.2 11.8 95.5 4.5
Car ownership
Yes 80.7 19.3* 97.3 2.7* 85.0 15.0 97.0 3.0*
No 75.7 24.3 88.2 11.8 85.2 14.8 91.0 9.0
Townsend index
Quintile 1 (most affluent) 80.2 19.8 97.8 2.2* 86.2 13.8* 96.9 3.1*
Quintile 2 79.3 20.7 96.3 3.7 86.4 13.6 97.1 2.9
Quintile 3 78.6 21.4 96.4 3.6 82.2 17.8 95.7 4.3
Quintile 4 80.5 19.5 96.3 3.7 83.9 16.1 95.9 4.1
Quintile 5 (most deprived) 81.9 18.1 93.9 6.1 86.5 13.5 93.1 6.9
Self-reported health
With condition 82.3 17.7* 97.4 2.6* 86.8 13.2* 96.1 3.9
Without condition 78.4 21.6 95.2 4.8 83.0 17.0 95.4 4.6
* Signifies significant trend across variable categories at P< .05.
Foster et al.International Journal of Behavioral Nutrition and Physical Activity 2011, 8:61
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warrants further research into what is the size of the
local neighbourhood in conjunction with cycling [19].
Ideally it would be helpful also include measures of
cycle path availability, alongside data on route choices
by cyclists, who might choose to use roads with lower
traffic volumes while cycling.
Future research should investigate the importance of
traffic and include other possible psychological journey
related correlates (e.g. attitude, confidence to cycling),
by gender and age [20]. Models should consider the
impact of environmental correlates at different distance
around home for different types of cycling (commuting
or leisure).
Conflict of Interest
The authors declare that they have no competing
interests.
Acknowledgements & Funding
We would like to thank the participants of the EPIC-Norfolk cohort. We also
would like to thank the staff of Norfolk’s local authorities and organizations
as well the Ordnance Survey who provided us access to data.
The work was funded by the British Heart Foundation Project Grant (BHF/
PG/03/045) and our own institutions. We thank the Ordnance Survey/EDINA
service who provided Road Network and Code Point data used in the
analysis. CF is funded by the British Heart Foundation. JP is funded by
National Institute for Health Research and NW is funded by the Medical
Research Council. NW and JP work under the auspices of the Centre for Diet
and Activity Research (CEDAR), a UKCRC Public Health Research Centre of
Excellence. Funding from the British Heart Foundation, Department of
Health, Economic and Social Research Council, Medical Research Council
and the Wellcome Trust, under the auspices of the UK Clinical Research
Collaboration, is gratefully acknowledged.
Author details
1
Department of Public Health, University of Oxford, UK.
2
Medical Research
Council Epidemiology Unit and Centre for Diet and Activity Research
(CEDAR), Institute of Public Health, Cambridge, UK.
Authors’contributions
CF & JP conceived of the study, and participated in its design and
coordination and helped to draft the manuscript. NW participated in its
design and coordination and helped to draft the manuscript. All authors
read and approved the final manuscript.
Received: 3 March 2011 Accepted: 10 June 2011
Published: 10 June 2011
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Table 2 Odds ratios (95% CI) for reporting leisure and commuter cycling in past month by quartiles of Road Traffic
Volume Index Score
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RTVIS within 500 m
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CI, Confidence Intervals; RTVIS Road Traffic Volume Index Score.
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doi:10.1186/1479-5868-8-61
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Foster et al.International Journal of Behavioral Nutrition and Physical Activity 2011, 8:61
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