<aside> ✍🏼 This chapter is authored by Manu Konchady
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While most cyclists do not spend a lot of time calculating the risks of riding a bicycle on each ride, it is worth the effort to lower the risks as far as possible. Some of the reasons for a cycling accident include road rage, dealing with an aggressive dog, road conditions, or a mechanical failure of the bicycle. Listing all possible reasons or causes for an accident is impractical and the best that a rider can do to avoid an accident, is to ride in a manner which will minimize the risk to the largest extent possible.
If you have been riding for a year or more, you may assume that accidents are what happens to “other” riders, until you have an accident. On the other hand, there are long time cyclists who have never been involved in a serious accident. While both cases are likely, cycling does have a measurable risk.
Ronald Howard defined the “micromort” to compare the riskiness of activities. An activity with one micromort of risk is an activity with a one in a million chance of death. For example, skydiving has a 8 micromort risk per jump based on the prior 413 deaths from 48.6 million jumps while climbing Mount Everest has a 75,000 micromort risk (about 300 deaths from 4000 attempts). We can use a similar measure to evaluate the risk of cycling. If there are $x$ fatalities from $y$ million rides, then cycling has a risk of $x\over y$ micromorts. However, a cycle ride can last much longer than a skydive and therefore the riskiness of a ride will also depend on the duration of the ride.
The U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) reported 630 cyclist deaths from about 4.1 billion rides in 2009 or a risk of 6.5 micromorts [1]. Oddly enough, most of the cycling fatalities (about 70%) occurred at non intersections and during the daytime. Almost three fourths of the fatal accidents occurred in urban areas and close to 90% of the riders involved in these accidents were males. Besides the odds of being involved in a fatal accident, a cyclist has a much higher chance of being injured in an accident. The same study from NHTSA reported 51,000 accidents with injuries or about 80 times the number of fatal accidents. Accidents with injuries may not be fatal but can vary with severity from the simple bruise to a major fracture or worse. Nonetheless, the risk of being involved in any type of accident is of concern to all cyclists.
One of the reasons that cycling appears risky is that a rider appears vulnerable and does not have any type of protection in an accident unlike other vehicles (see Figure 2.1). Without a protective steel cage to protect a cyclist, the impact from a fall or collision will be absorbed by some part of the body leading to an injury or worse.
A slightly older study [2] of the risks in all modes of transportation found that cycling was not as risky as some other modes of transportation. The study estimated the number of fatalities in terms of the number of deaths per 100 million person trips and defined six primary travel modes: passenger vehicle (passenger car, sport utility vehicle, van, or light truck), motorcycle, walking, bicycle, bus, and all other vehicles (e.g., large truck, motor home, taxi, limousine, or hotel/airport shuttle). Motorcyclists had the highest number of fatalities (500+) per 100 million person trips followed by other vehicle occupants (28), bicyclists (21), pedestrians (14), passenger vehicle occupants (9) and bus riders (0.4).
While riding a bus is clearly much safer than riding a bicycle, the risk of cycling is much lower than the risk of riding a motorcycle. You would assume that most of the serious cycling accidents (involving surgery and requiring intensive care) are due to collisions with larger vehicles on the road. Surprisingly, a study [3] of 2500 serious cycling accidents at San Francisco General Hospital found that over half of these types of accidents did not involve a car, but instead were possibly due to a cyclist avoiding a pedestrian, a pothole, or some other road obstacle. Still, a collision with a car or some other heavier vehicle always resulted in a fairly serious injury. Some observers also claim that not all bicycling accidents are reported and therefore cycling is actually more risky than what statistics reveal. With no clear trends and insufficient data, any conclusion is premature and the risks of cycling will remain.
One of the frequently cited deterrents for using cycling as a mode of transportation is safety [4]. These concerns are legitimate since the accident rate for cycling is still relatively high. However in countries like the Netherlands and Denmark with an extensive infrastructure and a relatively large number of cyclists, the accident rate is lower than in countries where cycling is not as popular. This is a catch-22 situation where it is likely that cycling will become safer with larger numbers of cyclists, but few ride bicycles because it is perceived as unsafe.
Measuring Safety When comparing the risks of different modes of transportation, a common measure is the number of fatalities per million or billion kilometers travelled. Air, train, and bus travel are among the safest modes of transportation using this measure at 0.05, 0.4, and 0.6 deaths per billion kilometers travelled respectively [5]. Motorists, cyclists, pedestrians, and motorcyclists have a much higher risk at 3.1, 44, 54, and 109 deaths per billion kilometers travelled.
However, a more fair comparison would use the time spent travelling instead of distance covered, since both pedestrians and cyclists cover much smaller distances than a plane or train. The time spent commuting on a road maybe the period of highest risk during a day spent at an office or at home. The accident rate for a mode of transportation can be defined as -
$Accident\space Rate\space ={\space No.\space of\space fatalities\space or\space injuries\over Exposure\space (kilometers\space or\space hours)}$
If the accident rate is described in terms of the number of fatalities per billion hours travelled, then the bus is safest mode of transportation followed by plane, train, car, walk, cycle and motorcycle. The time spent travelling is computed based on the average speed of a mode of transportation. While accidents involving a fatality are likely to be reported accurately, minor accidents are frequently under reported. Without accurate records of all types of bicycle accidents, measuring cycle safety will be inexact.
While many cities worldwide have policies to encourage cycling, the perception that cycling is an unsafe mode of transportation will hinder such objectives. If citizens do not feel cycling is safe, then few riders will take on the additional risk. At the same time, there is an inverse relationship between the number of cyclists and the number of accidents. The European Cyclists’ Federation claims that countries with the highest number of cyclists tend to have the best safety record. Encouraging cycling in a city with few cyclists is a quandary out of which there appears no easy solution.