Cycling on Milwaukee Avenue at Grand Avenue and Halsted Street, one of the most crash-likely intersections on Milwaukee Avenue.
Someone asked me on Twitter: “What’s more dangerous, biking with no helmet or driving with no seatbelt?” It’s an odd comparison, but I decided to try to crack the question.
Here’s my answer:
If your definition of “dangerous” is “the likelihood that you’ll receive an injury while traveling in/on the vehicle”, assuming that the likelihood of being in a crash is the same*, then you are more likely to sustain an injury while cycling while wearing a helmet than while driving or being a passenger in a car while wearing a seatbelt.
Here’s the data, for crashes in Chicago in 2007-2010:
Table 1: Yes, recorded to be wearing a helmet while bicycling
| Injury Type | Frequency (each number is a person) | Percent of total |
| No injury | 3 | 7.32% |
| Possible injury | 6 | 14.63 |
| Non-incapacitating injury | 26 | 63.41 |
| Incapacitating injury | 6 | 14.36 |
| Fatality* | 0 | 0 |
| Total | 41 | 100% |
A value of 0 fatalities in four years for people wearing a helmet absolutely DOES NOT mean that a helmet prevented a fatality. The “contrary” data for “Recorded to not be wearing a helmet or having safety equipment” shows that there was 1 fatality in four years – the data do not suggest that the fatality would be prevented if the person was wearing a helmet. The sample size is so small that this data is meaningless.
Table 2: Yes, recorded to be wearing a seatbelt as driver or passenger
| Injury Type | Frequency (each number is a person) | Percent of total |
| No injury | 423,096 | 89.42% |
| Possible injury | 21,667 | 4.58 |
| Non-incapacitating injury | 23,956 | 5.06 |
| Incapacitating injury | 4,338 | 0.92 |
| Fatality | 93 | 0.02 |
| Total | 473,150 | 100% |
*I don’t think we can determine the likelihood of being in a crash when riding a bicycle because we don’t know the “device miles traveled” of Chicago cyclists. It’s probably possible to approximate the number of vehicle miles traveled by drivers in Chicago, though; I’m not sure about passengers.
Download the data for this article, which includes these additional tables:
- Bicycling: All injuries
- Bicycling: No safety equipment or helmet wearing
- Bicycling: Unknown usage of safety equipment
- Auto: All injuries
- Auto: No safety equipment or helmet wearing
- Auto: Unknown usage of safety equipment