12th September 2014, Volume 127 Number 1402

Colin F Clarke

Wang et al responded1 to my article2 by detailing a number of points that merit additional consideration to provide for a better understanding of the outcome from the New Zealand helmet law.

They state: Since the NZ MHL went into effect on 1 January 1994, this study sheds no light on the cycling environment in a 6-year window around the MHL.

The articles provided cyclist and pedestrian fatality data for each of the 6 years as this was readily available and indicates an improving road safety situation, with a reduction for pedestrians 238 to 138 (1991–93 compared to 1994–96), down by 21%.

Census information3 shows travel to work details from 1991 to 1996 having a reduction from 5.39% to 4.04%, a relative reduction of 25%.

Census details of cycling to work levels:

1976 – 3.4%
1981 – 5.46%
1986 – 5.59%
1991 – 5.39%

(helmet law 1994)

1996 – 4.04% (75% of 5.39)
2001 – 3.12% (58% of 5.39)
2006 – 2.52% (47% of 5.39)
20134 – 2.2% (41% of 5.39)

Wang el al state: In fact, there was a 67% decline in serious traumatic brain injury (TBI) comparing data for the years nearest the helmet law (1988–1991 vs. 1996–1999).

New Zealand road fatalities were reduced by 28% during the period. In 1995 NZ adopted the campaign strategy used by Transport Accident Commission (TAC) in Victoria, Australia. The key priorities were anti drink-driving and deterring driving at excessive speed that helped to reduce road deaths by 49%, from 777 in 1989 to 396 in 1992.

The TAC data from Victoria5 for head injury claimants by bicyclists involved in motor vehicle accidents, detailed that most were age less than 18 years of age, pre cycle helmet law, for the period 1987–1989, see Table 1.

 


Table 1. Transport Accident Commission data from Victoria, Australia, for the period 1987–1989

 

Age (years)

Head (Hd)

Concussion (Con)

Hd + Con

Total claims

Percent Hd+Con

0–11

12–17

18+

56

82

40

27

45

22

83

127

62

514

1162

812

16.15

10.93

7.64

Total

178

94

272

2488

10.93

 

The younger age groups had higher rates of head injury. For New Zealand, survey information suggests the largest reductions in cycling were for the age group 5–17 years,6 reducing from 80 minutes per week in 1989/90 to 46 minutes in 97/98. Tin Tin et al report: The rate of traumatic brain injuries fell from 1988–91 to 1996–99; however, injuries to other body parts increased steadily.7

A 2001 study by Robinson re-evaluated NZ data,8 finding that the reduction in head injuries per limb injuries, for crashes not involving motor vehicles injuries, was part of a larger downward time trend and bore no direct correlation to the dramatic increase in helmet-wearing following the introduction of the helmet law.

Robinson concluded: Because the large increases in wearing with helmet laws have not resulted in any obvious change over and above existing trends, helmet laws and major helmet promotion campaigns are likely to prove less beneficial and less cost effective than proven road-safety measures.

See Figure 1 below from http://en.wikipedia.org/wiki/Bicycle_helmets_in_New_Zealand

 

Figure 1

 

Wang et al give the impression in their Figure 1 of a major benefit by selecting the injury rates and percent helmeted. They provided two graphs, one serious injuries and the other serious TBI, both per 100,000 hours travelled. The first shows a reduction from about 25 to 21 for the claimed serious injuries, down by about 17%. The second for serious TBI shows a reduction from about 3.4 to 1.2 and they claim a 67% reduction. Viewing side by side gives the impression of a major reduction in serious TBI compared with other general serious injuries, 67% v 17%.

In the 2012 article, Table 4 details serious injuries per 100,000 hours travelled for the same periods, reducing from 10.27 to 4.86, down by 53%. Also Table 4 details overall injuries per 100,000 hours travelled, reducing from 25.61 to 21.38 and then increasing to 30.74. It seems that Wang et al have used the incorrect data. Using serious TBI v serious injury data would have shown roughly a 67% v 53% reduction. Care is required in considering data on TBI in that the criteria for admissions can change due to several factors.9

Wang et al make a number of other points they consider I should have addressed but unfortunately the length of the article was limited to 3000 words and this restricted its content. The main findings—failed in aspects of promoting cycling, safety, health, accident compensation, environmental issues and civil liberties. It is estimated to cost about 53 lives per year in premature deaths and result in thousands of fines plus legal aspects of discrimination in accident compensation cases—are certainly valid in general terms, despite it having some shortcomings. More accurate calculations can be made.

Recently the UK Cyclists' Touring Club (CTC) stated10: However CTC is not only concerned about the harmful effects of mandatory helmet use. By creating exaggerated perceptions of the risks of cycling, even voluntary helmet promotion campaigns have been found to deter some people from cycling. Given that the health benefits of cycling outweigh the risks by around 20:1 (one recent study put it at 77:1), it can be shown that only a very small reduction in cycle use is needed for helmet promotion (let alone helmet laws) to shorten more lives than helmets themselves could possibly save, regardless of how effective helmets might be.

Recent data11 released since the paper's publication show NZ bicycle travel to school 5–17year age group is down from 14.2 million journeys in 1989/90 to 3.3 million in 2009–13. New Zealand's population increased 31.2% from 1990 to 2013. The incidents of ischaemic heart disease, stroke and diabetes that cycling may help to prevent are approximately 600+ per 100,000 population.12

The argument put by Wang et al of a reduction in TBI are largely explained by the combined effects of decreased cycling levels and improved road safety post law. The increase in the accident rate and all body injuries per cyclist plus the negative long-term health consequences of discouraging cycling have to be seriously considered.



Author Information

Colin F Clarke

(Colin F Clarke studied mechanical engineering at Huddersfield Polytechnic. He qualified in 1970 as a British Cycling Federation coach. He has been a cyclist for more than 40 years and has worked as a road safety instructor teaching children how to ride bicycles safely. He has cycled in more than 20 countries, including approximately 8000 kilometres in NZ.)

Correspondence Email

Colin@vood.freeserve.co.uk

References

1. Wang J, Olivier J, Grzebieta R. Response to 'Evaluation of New Zealand's bicycle helmet law' article. N Z Med J. 2014 Feb 14;127(1389):106-8. http://www.nzma.org.nz/journal/read-the-journal/all-issues/2010-2019/2014/vol-127-no.-1389/5988

2. Clarke CF. Evaluation of New Zealand’s bicycle helmet law. N Z Med J. 2012;125(1349). http://www.nzma.org.nz/journal/read-the-journal/all-issues/2010-2019/2012/vol-125-no-1349/article-clarke

3. Tin Tin S, Woodward A, Thornley S, Ameratunga S, Cycling and walking to work in New Zealand, 1991-2006: regional and individual differences, and pointers to effective interventions. International Journal of Behavioral Nutrition and Physical Activity 2009;6:64 doi:10.1186/1479-5868-6-64.

4. http://www.stats.govt.nz/Census/2013-census/data-tables/tables-about-a-place.aspx?request_value=24439&reportid=14&tabname=Transport accessed 21.8.2014

5. TAC data provide to C Clarke, 1993.

6. Mandatory bicycle helmet law in New Zealand, http://www.cycle-helmets.com/zealand_helmets.html, accessed 21.8.2014.

7. Tin Tin S, Woodward A, Ameratunga S. Injuries to pedal cyclists on New Zealand roads, 1988-2007. BMC Public Health. 2010;10:655.

8. http://en.wikipedia.org/wiki/Bicycle_helmets_in_New_Zealand accessed 21.8.2014

9. McNaughton H, Wadsworth K. Assessing the accuracy of hospital admission and discharge diagnosis of traumatic brain injury in a New Zealand hospital. http://www.ncbi.nlm.nih.gov/pubmed/10917079

10. http://www.ctc.org.uk/campaign/cycle-helmets-evidence accessed 21/.9.2014

11. New Zealand Household Travel Survey 2010-2013, http://www.transport.govt.nz/assets/Uploads/Research/Documents/Comparing-travel-modes-2014-y911-final-v4.pdf accessed 26.8.2014

12. Overall health of Pacific peoples in New Zealand, Table 4. http://www.stats.govt.nz/browse_for_stats/people_and_communities/pacific_peoples/pacific-progress-health/overall-health.aspx#young