Risk of Head Injury

A closer look at risk of head injury for commute trips in Toronto

Following up on a comment I received on an article I wrote About Safe Cycling

OK, in Ontario, 49% of head injuries are related to motor vehicle involvement and 2% of head injuries occur to cyclists. For the comparison of these two percentages to have any relevance at all, the general population would, on average, have to spend as much time on a bicycle as they do in or around vehicles.

I received similar comments on Social Media about the smaller modal share of cycling skewing the results into making cycling appear safer.

Let’s find out.

Constraints

Cycling measurements are often broken down into trip purposes like commutes, utility, and recreation trips. Conversely, driving statistics are typically measured by commutes only.

Cycling is unique in that the highest consideration of riding for a variety of purposes — particularly commutes — is more likely to occur in cities where trip start points and destinations are close. For this reason, I’m going to apply the averages from the provincial injury report to my home census area: Toronto, where 68.9% of cycling commute trips were under 5km in 2011. Car commute trips were typically 2–3 times further.

Daily Average Head Injuries

In the report “Major Head and Spinal Cord Injury Hospitalizations in Ontario, 2001–2002”, there were 4,066 total reports of head injuries across Ontario. 2008 recorded head injuries related to motor vehicle use, and 54 related to cycling. This is the report that indicates less than 2% of head injuries occur to cyclists.

Over the course of a year, in Ontario, this forms a daily average of:

  • 0.15 daily cycling head injuries
  • 5.50 daily driving head injuries

Daily Commute Trips in Toronto

According to City of Toronto statistics, from data taken from the Statistics Canada, 2006 Census:

  • 19,780 Torontonians cycle to work
  • 644,400 drive to work, either by car, truck, van, motorcycle, taxicab as driver or passenger

Assumption: Toronto Injuries

One hurdle to overcome at this point is how to determine an average daily head injury rate for the city of Toronto. For the purposes of this article, I have to make a judgement call. I’ve decided to do it this way: Since in 2006, Toronto’s population represented about 20.58% of Ontario’s population, I’m applying this ratio to the provincial head injury rate to estimate Toronto’s rate.

  • 0.15 x 20.58% = 0.0305 daily cycling head injuries
    about 1 every 33 days
  • 5.50 x 20.58% = 1.1324 daily driving head injuries
    a little more than 1 per day.

Risk of Commute Head Injuries in Toronto

Factoring in our calculation for Toronto’s average daily head injuries, we get:

  • 0.0305 / 19,780 = 0.0000015 daily head injuries
    per cycling commute trip, approximately 1 for every 648525 trips.
  • 1.1324 / 644,400 = 0.0000018 daily head injuries
    per driving commute trip, approximately 1 for every 569057 trips.

This suggests that per commute trip, despite cars having seat belts, air bags, and other safety features…


Driving has a 14% higher daily risk of head injury than cycling when commuting in Toronto.

So remember, Toronto area commuters: When setting off in the car for work, put on that driving helmet.