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City Cycling:

Risks and Benefits

By Martha Williams

September 24, 2007



Bicycling is both a fun leisure and beneficial fitness activity.  It’s a simple way to commute, avoid the hassles of driving, and get a workout all at the same time.  But there are many issues and questions that come long with bicycling on roadways.  For example: whether there are lanes designated for bicyclists, whether the roadways are safe for bicyclists, or whether car fumes are more destructive than the exercise is beneficial. 


Cities throughout the United States and around the globe are constructing more bicycle lanes every year in an attempt to make cycling a safer, easier mode of transport and leisure activity.  The general idea behind the addition of bicycle lanes addresses safety, health, economical and environmental issues.  The ideas behind the lanes are: that current bicyclers will be safer riding on the roads; that more people will be encouraged to ride their bicycles to work or for leisure, and therefore cut down on gas expenses, air pollution, and water pollution from runoff; that greater physical and mental health will be promoted; and that rising trends in obesity may be slowed by cutting down on car usage in the U.S.



Bike parking in Amsterdam

Photo found at:




In a May 2006 article by Kevin Helliker of the Chicago Sun Times, cycling is promoted as a chic trend which both saves gas and builds lung power.  Helliker discusses the growing appeal of city-workers commuting to work by bike, especially among affluent professionals.  Besides the health benefits, commuting by bike offers a chance for exercise without taking extra time and “it saves on the growing cost of fuel and even carries a certain cachet at the office” (  Along with this trend comes the necessity for showers at work places for cycling commuters, and for bike stations.  Bike stations are being built in many large cities as a place to store bicycles during the day and as a place for cyclists to shower before heading to work. 


Cities are also competing to see who can be the most cycle friendly by constructing new bicycle lanes, building bicycle stations and other lock-up racks.  Of course, this is all in an effort to also reduce traffic jams and pollution.  Helliker is challenging these environmental reasons, though, and suggesting that cycling is more of a fashionable trend which cities are playing to in order to gain popularity.  Not that they don’t care about the environment, though.  Allison Krueger, a 26-year-old from Chicago, states in Helliker’s article that, “Biking is definitely fashionable in Chicago”, an addition to her statements of the many benefits of cycling to work (  

Cycling definitely is a growing trend.  In 2003 New York City opened a 17-mile bike trail on the West Side of Manhattan, bike paths on bridges connecting Manhattan and Brooklyn, and has since seen a 50% increase in cyclist since 2000.  According to the advocacy group Transportation Alternatives there are now 120,000 cyclists a day in New York City ( 


Helliker also mentions the downsides of cycling in his article, namely the physical dangers of riding with traffic.  According to an article in the 2003 American Journal of Public Health, “a cyclist in America is 12 times likelier than a car occupant to be killed”.  However, federal statistics state that the number of cyclists killed in America fell nearly 10% during the decade ending with 2004.  Also, some studies claim that as the number of cyclists increase, collisions with cars decline because motorists become more aware of cyclists’ presence.  For example, according to Transport of London, as cycling increased 100% from 2000 to 2005 in London, the accident rate for cyclists fell 40% in ( 




One more argument for cycling that Helliker refers to is the possibility of health benefits.  According to John Pucher of Rutgers University, cycling builds muscle, deepens lung capacity, lowers heart rate and burns calories.  He says, “The health benefits of cycling outweigh the health risks by [a ratio of] 2-1, if not something like 5-1” ( 


According to The President’s Council on Physical Fitness and Sports, biking is a form of “aerobic” or cardio respiratory exercise.  Biking strengthens your heart and lungs “by making them work hard to deliver oxygen and nutrients throughout your body” (Bicycling for Exercise and Pleasure).  Also, bicycling can help you lose weight, firm muscles and have a healthier lifestyle overall.  However, in order to achieve these physical benefits from cycling you have to follow the guidelines necessary for any aerobic exercise: “at least three workouts per week, for 20-40 minutes, at a fairly vigorous intensity” (Bicycling for Exercise and Pleasure).


A website created by the University of Central Florida’s Environmental Management group promotes bicycling for both its physical and mental health benefits.  The site claims that in a society of high health problems such as diabetes and heart disease, “urban driving exacerbates these disorders, while bicycling is preventative or therapeutic for all of them” (  In addition to this benefit, bicycling helps a person to develop balance, coordination and strength.  It tones muscles, strengthens bones, and burns calories.  And it’s good for your mental and emotional health, too.  While a large number of people in the US deal with depression, violence or stress, exercise such as bicycling can be therapeutic.  The site claims that, “Driving stresses; bicycling relaxes.  Road rage is set off by car traffic, not bicycles” (  I would like to suggest that this is a highly optimistic view of bicycling.  While I agree that research and personal experience advocate that bicycling can be therapeutic and helpful, it can certainly be just as stressful as driving.  Like car drivers, bicyclists also have to pay attention to traffic and deal with the mistakes of others.




The reverse of this way of thinking (of the University of Central Florida’s website) addresses the health concerns that go with bicycling: namely, the possibility of pollutants entering your body as you bicycle through traffic. According to Bicycle Universe, an online information site for bicycle users, “pollution by cars causes lung cancer, respiratory problems, urban smog, and acid rain” (  This site explains the concept of ground-level ozone--the matter that causes hazy smog and respiratory problems-- and how cars create pollution by contributing to its growing amount.  According to the site, “Ozone pollution has become widespread in cities in Europe, North America, and Japan as auto and industrial emissions have increases”, and, “levels typical in many cities can irritate the respiratory tract and impair lung function, coughing, shortness of breath, and chest pain” (  The site goes on to say that “Evidence also suggests ozone exposure lowers the body’s defenses, increasing susceptibility to respiratory infections” (  This seems to make perfect sense that riding behind a car emitting fumes could easily damage your lungs, but there is at least one study that suggests this is not what you should be most concerned about.


          In a study by the University of Roskilde in Denmark, researchers examined the claim that cycling in heavy traffic is unhealthier than driving a car.  In their experiment, teams of two cyclists and two car drivers were given personal air samplers and instructed to drive for 4 hours on two different days in Copenhagen’s morning traffic.  According to the study report, the “air sample charcoal tubes were analyzed for their benzene, toluene, ethyl benzene and xylene (BTEX) content and the air filters for particles (total dust)” (Rank, Folke, & Jespersen, 2001).  The study found that concentrations of BTEX and particles in cars were 2-4 times higher than in the cyclists’ breathing zone.  Even after taking into account the increased respiration rate of cyclists, car drivers appeared to be more exposed to airborne pollution than cyclists (Rank, Folke, & Jespersen, 2001).

Because of their world class cycling infrastructure, the roads of Copenhagen are safer and more environmentally friendly.


Photo found at:






















However, in an earlier study by the Municipal Health Service of Amsterdam, research suggested that the uptake of NO2 was clearly higher for bicyclists than for car drivers.  This study followed volunteers through various routes of the inner city for two weeks and measured CO, NO2, benzene, toluene and xylenes in the personal air samples given to each volunteer.  The researchers' results showed that uptake of CO, benzene, toluene and xylenes were much higher for car drivers, but that uptake of NO2 was higher for cyclists (van Wijnen, Verhoeff, Jans, & van Bruggen, 1995).


So what is a bicyclist to do with such conflicting information?  Continuing to weigh the advantages of health benefits and risks of bicycling on the city streets is the only option possible at this point.  As bicycling becomes more and more popular, it is likely that more research will evolve and attempt to answer this question.  For now, however, pollutants are obviously not the only threat to cyclists; in fact they are not nearly as much of a concern as immediate physical danger cyclists face every day as they weave through busy streets around the globe.


A study performed by transportation engineers at the University of Texas at Austin examined the interactions of drivers and bicyclists on Texas roads.  The study was performed in cities such as Austin, Houston, and San Antonio where the government is considering how to increase bicycle lanes as part of meeting federal requirements of the Clean Air Act.  The study found that “having painted bike lanes on streets and roads helps both commuters stay in safer, more central positions in their respective lanes” (  Randy Machemehl, director of the university’s Center for Transportation Research said that “Without a marked bike lane, there appears to be a lot of uncertainty about how much space each person needs—even when adequate road space is provided” (  The Texas Department of Transportation provided $114,000 for the study which was conducted on two- and four-lanes roadways with bike lanes, and included 31 paid and volunteer cyclists.    The CTR engineers chose volunteer cyclists of varying ages, genders, and cycling experience for observation in order to ensure results that could be generalized to varying situations and locations.  Eight thousand “passing events” were studied between February and March of 2005 in an attempt to understand the relationship between driver’s perceptions of bicyclists and safety for cyclists on the road. 


Researchers found that cyclists on a road absent of a marked bicycle lane tended the hug to curb “dangerously close”, while cyclists on roads with a striped lane the same width area rode more safely.  Similarly, researchers also found that in the absence of a marked lane drivers tended to veer “so far in an apparent effort to avoid collision that they swerved a full four feet into the next motorists’ lane” (  Whereas, with a striped bike lane, drivers who still swerved only encroached about 40 percent as far.



Previous studies had suggested other benefits of marked bicycle lanes, which the University of Texas engineers had hoped to build on.  Some research had shown that cyclists are more likely to stop at intersections and obey other general traffic rules when roads are marked to include them in traffic.  Also, cyclists are less likely to ride on sidewalks if there is a lane provided for them.  When they ride on sidewalks, studies have shown “that it increases their accident risk 25 times” because turning cars are unaware of their presence.  Bike lanes reinforce the concept that bicyclists are supposed to behave like other vehicles, and make life safer for everyone involved as a result”, says Ian Hallett, a CTR graduate research assistant (


In a recent study by the Department for Trauma and Hanover Medical School of Germany, researchers set out to analyze the injury situation of bicyclists in Germany in an effort to create a basis for effective preventive measures.  The study looked at 4,264 injured bicyclists from 1985 to 2003, 55% of which were men.  The average age of bicyclists in the study was 52 years.  The bicyclists were divided depending on what type of collision they had: cars (65.8%), trucks (7.2%), other bicyclists (7.4%), standing objects (8.8%), multiple opponents or objects (4.3%), and other (6.5%).  An interesting facet of this study was that the helmet use rate was only 1.7%.  Also, of the 4,264 bicyclists, fifty-five percent used bicycle lanes before the crash.  The mean Maximum Abbreviated Injury Scale/Injury Severity Score (ISS) was 1.45 or 3.9.  This score was higher in both bicyclists who rode without a helmet in bicyclists who had not used bicycles traffic lanes.  The researchers concluded from their study that head and extremities are at a high risk for injuries, and that two-thirds of the head injuries in the study could have been prevented by helmet use.  The researchers recommended “more consequent helmet use and an extension of bicycle traffic lanes for a better separation of bicyclists and motorized vehicles would be simple but very effective preventive measures” (Richter, Otte, Haasper, Knoblock, Probst, & Westhoff, et. Al, 2007).



In a study performed by the Department of Psychology at the University of Helsinki, Finland, researchers studied 188 bicycle-car accidents in four cities by reconstructing the movements of those involved in an effort to assess detection of the other party in each accident.  In 37% of collisions, neither the driver nor the cyclist realized the danger present or had sufficient time to yield.  In the other collisions, either the driver (27%), the cyclist (24%) or both (12%) did something to avoid the accident.  Two underlying factors were identified by the researchers as mechanisms which impacted the accident.  First, “allocation of attention such that others were not detected, and second, unjustified expectations about the behavior of others” (Räsänen & Summala, 1998).  The most frequent accident type was at a crossing where a driver was turning right and a bicyclist was continuing straight.  According to the researchers, this finding supported an earlier finding that drivers turning right hit cyclists because they looked left for cars during the “critical phase” (Räsänen & Summala, 1998).  Only 11% of drivers noticed the bicyclist before impact, while 68% of bicyclists noticed the driver before the accident.  Even more interesting is that 92% of those bicyclists who noticed believed the driver would give way as required by law. 


All bicyclists need not fear, though.  Bicycling is continually becoming a safer mode of transport.  According to P. Jacobsen, a Public Health Consultant from Sacramento, California, a motorist is “less likely to collide with a person walking and bicycling if more people walk or bicycle” (Safety in numbers, 2003).  As a result of his conclusions, Jacobsen suggests that public policies that “increase the numbers of people walking and bicycling appear to be an effective route to improving the safety of people walking and bicycling” (Safety in numbers, 2003).  Jacobsen examined three published analyses of collision rates that showed declines with increases non-linearly in the numbers of people walking or bicycling.

          A related study in Australia performed by the University of New England in Armidale, New South Wales, sought to find a similar tendency in safety in numbers for walkers and bicyclers.  This retrospective study compared three different datasets concerning fatality and injury: fatalities and amount of cycling in Australian States during the 1980s; fatality and injury rates over time as bicycling levels increased in Western Australia; and, deaths, serious head injuries and other injuries to bicyclists and pedestrians in Victoria.  The results of the study suggested that “the risks of fatality and injury per cyclist are lower when cycling is more prevalent” (Robinson, 2005).  During the time of the study in Western Australia, hospitalization rates per 10,000 bicyclists fell from 29 to 15, and reported deaths and serious injuries from 5.6 to 3.8 as the amount of bicyclists increased.  From this study, the researcher determined that the exponential growth rule which suits other countries also fits the data of Australia.  “If cycling doubles, the risk per kilometer falls by about 34%, conversely, if cycling halves, the risk per kilometer will be about 52% higher”, says D.L. Robinson, the researcher of the Australian project.


          Bicycling has long been a popular leisure activity, and in recent decades a view of the bicycle as a fashionable and useful mode of transportation has emerged.  This new view of the bicycle has the possibility to transform the world we live in.  Many countries are already bicycle-friendly and full of urban planning designed to protect and promote bicycling.  If this trend continues many outcomes are possible: fewer greenhouse gases will be emitted into the atmosphere due to a lower dependence on automobiles; there will be healthier citizens worldwide who exercise while they move throughout cities; and, hopefully the world will be full of happier people who feel safe bicycling on roadways.  As bicycling becomes more and more popular and more bicyclists line the roads, I think that the predictions of Jacobsen will certainly come true.  A greater awareness of cyclists and appreciation for their presence has the opportunity to emerge during this time and in doing so promote healthier lifestyles for anyone who wants to join the revolution.








Jacobson, P.L. (2003, September). Safety in numbers: more walkers and bicyclists, safer walking and bicycling. Injury prevention: journal of the International Society for

Child and Adolescent Injury Prevention, 9, 205-0.  Retrieved September 23, 2007 from PubMed.

Rank, J., Folke, J., & Jespersen, P.H. (2001, November). Differences in cyclists and car drivers exposure to air pollution from traffic in the city of Copenhagen. The Science

of the total environment, 279, 131-6. Retrieved September 23, 2007 from PubMed.

Räsänen, M., & Summala, H. (1998, September). Attention and expectation problems in bicycle-car collisions: an in-depth study. Accident; analysis and prevention, 30,

657-66. Retrieved September 23, 2007 from PubMed. 

Richter, M., Otte, D., Haasper, C., Knoblock, K., Probst, C., & Westhoff, J., et al (2007, May). The current injury situation of bicyclists--a medical and technical crash

analysis. The Journal of Trauma, 62, 1118-22. Retrieved September 23, 2007, from PubMed.

Robinson, D.L. (2005, April). Safety in numbers in Australia: more walkers and bicyclists, safer walking and bicycling. Health promotion journal of Australia: official journal

of Australian Association of Health Promotion Professionals, 16, 47-51. Retrieved September 23, 2007 from PubMed.

The President’s Council on Physical Fitness and Sports. (1987). Bicycling for Exercise and Pleasure. Washington, DC: U.S. Government Printing Office.

van Wijnen, J.H., Verhoeff, A.P., Jans, H.W., & van Bruggen, M. (1995). The exposure of cyclists, car drivers and pedestrians to traffic-related air pollutants. International

archives of occupations and Environmental health, 67, 187-93. Retrieved September 23, 2007 from PubMed.



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