Helmet law effects (ridership)

From ChapmanCentral

Effects of cycle helmet laws on ridership

Alberta

The Alberta survey compared a pre-law survey in 2000 with a post-law survey in 2004. The pre-law survey collected information at 99 sites in Edmonton.

In 2004 they decided to count cyclists at 23 of these sites (those with more than 10 cyclists in 2000), on the same weekday and at the same time periods as the pre-law survey. Fives sites were re-scheduled because of inclement weather. One couldn't be rescheduled, so they ended up with data for 22 sites. The post-law survey started in July, so none of the 22 post-law sites were schools.

From what I can gather, 699 cyclists were counted at those sites in 2000, but only 271 in 2004. The paper explains: "*Because we captured more information (for example, clothing color) on each cyclist, did not capture information on all cyclists, but only those passing by the research team, and recorded information on pedestrians in 2004, we cannot comment on the number of cyclists seen in 2000 and 2004 *."

Each site appears to have been recorded by 3 people – a controller and two observers. It wouldn't be worth designing a survey that recorded a site for less than an hour. So, 271 cyclists over at least 66 person hours of observation represents no more than 4 cyclists per person-hour of observation. It would not have been difficult to count all cyclists passing by, record whether adult, child or teenager and whether wearing a helmet and record additional details on selected cyclists.

We don't know what proportion the 271 cyclists represents of all cyclists that passed the observers, but I suspect (given the average of 4 cyclists per person hour) there weren't very many more. So, compared to 66 children and 98 adolescents recorded pre-law, the total of 13 children (80% fewer than pre-law) and 28 adolescents (71% fewer than pre-law) is pitifully small - a pretty good indication that the law discouraged cycling. This is backed up by the fact that the helmet law was for children and, post-law, children were a significantly lower proportion of total cyclists than pre-law.

You'd have expected that, after seeing these results, the authors would want to to do some follow-up, e.g. a survey in schools asking children if they cycle less because of helmet laws (as was found in a school survey in Australia). But instead, the authors of the paper concluded that Alberta should consider extending the law to adults - for more information and discussion see http://injuryprevention.bmj.com/cgi/eletters/12/4/262

Posted to Usenet by Dorothy Robinson

Nova Scotia

When the results of the survey were published in CMAJ, Malcolm Wardlaw wrote a letter that was published in the journal. It says:

"Their bicycle count data show a 40%–60% fall in the number of cyclists

after the law was passed, from 88 per day down to 33 or 52 per day. Their injury data show a sharp fall in total injuries in 1997, but for 1998/99 the number of injuries was higher than before the law (443 v. 416). The absolute number of head injuries has fallen by half, but so has the number of cyclists, although the total number of injuries has increased." *( http://www.cmaj.ca/cgi/content/full/167/4/337-b )

The authors replied:

"We sought to maximize the number of cyclists observed in a fixed

observation period. Due to availability of observers, we could not standardize observation times from year to year. Not surprisingly, we observed large variations in the number of cyclists per unit time, depending on the time of day, the day of the week, or the month. For example, during 1998 and 1999 we collected data almost exclusively during weekdays, which largely reflected adult commuter traffic." *(http://www.cmaj.ca/cgi/content/full/167/4/338)

Prof Mary L. Chipman then wrote a letter commenting:

"His study was designed to maximize the number of cyclists observed in a

fixed time interval, and he chose sites and circumstances accordingly. However, despite this effort to observe more cyclists, he actually observed fewer after legislation, so I am quite convinced that the number of cyclists has been dropping." * http://www.cmaj.ca/cgi/content/full/167/4/339)

These above two examples could be use to demonstrate that several published studies strongly suggest that the helmet laws discouraged cycling. This is particularly true for Alberta where the surveys used the same sites and observation times and instead of conducting any post-law surveys in inclement weather, rescheduled them in good e weather. Despite this, the number of child and adolescent cyclists counted fell by 80% and 71% respectively. Although we can't be certain that there were other child cyclists who passed the observers without being counted, they recorded only 0.2 child and 0.4 adolescent cyclists per observer per site. If more had passed by, surely they would have been able to record them!

Posted to Usenet by Dorothy Robinson