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Alberta's helmet law – children's cycling halved, injuries increased per cyclist

Includes a commentary on:
Bicycle helmet use and bicyclists head injuries before and after helmet legislation in Alberta Canada
Karkhaneh M, University of Alberta, 2011. (Karkhaneh, 2011)

Evidence on changes in cycle use and risk

A helmet law for Alberta

A helmet law for cyclists under 18 was introduced in Alberta, Canada, on 1 May 2002.

Edmonton – 59% reduction in children’s cycling by 2004

Cyclists were counted in Edmonton (a city in Alberta), in 2000 (pre-law) and 2004 (post-law). The percentage of cyclists under 18 fell from 26% in the pre-law survey, to 15% post-law (Hagel et al, 2006), suggesting that the law discouraged substantial numbers of youngsters from cycling. Compared to adults who were not required to wear helmets, children’s cycling (<13 years) fell by 59%, with a 41% reduction for teenagers aged 13-17 (Hagel et al, 2006).

At the time, great concerns were also expressed that injuries per cyclist had increased after the introduction of Alberta’s helmet law (BHRF, 1055).

Wider surveys – 56% reduction in children cycling and 27% reduction in teenagers, by 2006

Comprehensive survey results were published in 2011 in a PhD thesis (Karkhaneh, 2011).  The data were collated from observational studies of Albertan cyclists in several cities, involving 330 hours of pre-law observations in 2000, and 313 hours of observation post-law in 2006.

The survey showed a large and significant 56% decrease in children's cycling, confirming the large decrease in children’s cycling noted in the Edmonton survey, 2 years earlier.  The greatest decreases were at schools (68% decrease), on commuter routes (41% decrease) and in residential areas (37% decrease).

There was also a significant 27% decrease in teenage (13-17 years) cycling.  In contrast, there was a 21% increase for adults, who were not required to wear helmets. (Karkhaneh, 2011)

Increased risk for child and teenage cyclists after the helmet law

With such large decreases in children’s cycling, commensurate decreases would be expected in the numbers of children with cycling injuries.  Table 1 shows changes in cycle use and in average annual numbers of cyclists requiring emergency room treatment for non-head injuries over the 3 years pre-law (1999-2002) and post-law (2003-2006).

Table 1. Number of cyclists per hour from the observational surveys in Alberta (pre-law in 2000, post-law in 2006),
compared to numbers treated in emergency rooms (ER) for non-head injuries. From Karkhaneh, 2011

  Cyclists per hour Non-head injuries (ER) 1 Change in injuries relative
  Pre Post CRatio 2 Pre Post IRatio 2 to change in cycling 3
Children 3.56 1.58 0.44 1676.3 1762.0 1.05 2.37
Teenagers 1.92 1.41 0.73 870.3 1101.0 1.27 1.72
Adults 18+ 6.29 7.58 1.21 1846.7 2062.5 1.12 0.93

1 Average annual number of non-head injuries; 2 Post-law divided by pre-law; 3 IRatio divided by CRatio

The table paints a shocking picture.  With only 44% as many children cycling, there should have been only 44% as many injuries – i.e. 44% of 1676 = 744.  The observed post-law number of injuries – 1676 per year – is 2.37 times higher than would have been expected for the amount of cycling.  In contrast, the safety of adult cyclists (who were not affected by the law) improved. 

Thus, far from improving safety for children and teenagers, the risk of injury seems to have increased after Alberta introduced its helmet law.  Similar calculations (Tables 2 & 3), show increases in the risk of head and non-head injuries requiring ER treatment for both children and teenagers, as well as increased risk of head injuries for children, and non-head injuries for children and teenagers admitted to hospital.  In contrast, risks for adults generally decreased.

Unlike cyclists, there were substantial reductions in the risks of injury for pedestrians (Table 3).

Table 2.  Ratio of pre-law (1999-2001) and post-law (2003-2006) numbers of cyclists given emergency room (ER) treatment
or admitted to hospital per year – head and all cycling injuries –
compared to ratio of post vs pre-law cycle use.  From Karkhaneh, 2011

  Cyclist head injuries All cyclist injuries Injury vs cycle use
changes 1
  Pre Post Ratio Pre Post Ratio Head All
Cyclists – ER Treatment          
Children 739.0 577.3 0.78 2415.3 2339.3 0.97 1.76 2.18
Teenagers 230.0 253.0 1.10 1100.3 1354.0 1.23 1.50 1.68
Adults 18+ 476.3 504.0 1.06 2323.0 2566.5 1.10 0.88 0.92
Cyclists – hospital admissions          
Children 36.3 19.0 0.52 107.7 93.3 0.87 1.18 1.95
Teenagers 24.3 16.8 0.69 60.0 72.3 1.20 0.94 1.64

Adults 18+

56.7 51.8 0.91 206.7 258.3 1.25 0.76 1.04

 

1 Injury vs cycle use changes: calculated as the ratio of injury rates (post-law to pre-law injuries) divided by the change in cycle use
(ratio of cyclists per hour post-law cyclists to pre-law – 0.44 for children, 0.73 for teenagers and 1.21 for adults, see Table 1). 
Values less than 1 imply improved safety per cyclist, those greater than 1 imply greater danger.

Table 3.  Ratio of pre-law (1999-2001) and post-law (2003-2006) numbers of pedestrians given emergency room (ER) treatment
or admitted to hospital per year – head and all injuries – compared to ratio of post vs pre-law population counts by age group. 
From Karkhaneh, 2011

  Pedestrian head injuries All pedestrian injuries Injury vs population
changes 1
  Pre Post Ratio Pre Post Ratio Head All
Pedestrians – ER Treatment          
Children 87.7
47.3
0.54
267.3
162.0
0.61
0.54
0.60
Teenagers 39.3
37.0
0.94
220.0
206.3
0.94
0.88
0.88
Adults 18+ 188.0
187.3
1.00
867.3
929.0
1.07
0.88
0.95
Pedestrians – hospital admissions          
Children 20.3
13.0
0.64
48.0
31.3
0.65
0.63
0.64
Teenagers 16.7
11.25
0.68
32.0
24.8
0.77
0.63
0.72

Adults 18+

99.3
85.75
0.86
251.7
224.3
0.89
0.77
0.79

1 Injury vs population changes: calculated as the ratio of injury rates (post-law to pre-law injuries) divided by the change in population
(1.003 for children, 1.064 for teenagers and 1.128).  Values less than 1 imply improved safety per capita.

Conclusion

When changes in cycle use are taken into account, Alberta’s helmet law seems to have increased the risk of both head and non-head injuries.

Evidence of increased risk per cyclist seems paradoxical.  However, there is strong evidence that helmet laws lead to increased risk taking. For example, many males (Messiah et al, 2012) and cyclists accustomed to wearing helmets (Phillips, Fyhri and Sagberg, 2011) have been shown to cycle faster when wearing a helmet.  In addition, drivers were found to leave less room when overtaking helmeted cyclists (Walker, 2007).  UK researcher, Dr Ian Walker, was hit twice by vehicles when carrying out his research, both times when wearing a helmet (Eureka, 2006). With only 44% as many children cycling as before the law, it is also possible that relatively safe cycling activities were discouraged more than riskier types of cycling. 

Published analysis ignores changes in cycle use

Karkhaneh, 2011 ignores the large and obvious reduction in cycle use when discussing the effect of the law on injuries.  The thesis also makes light of the 56% overall reduction in children’s cycling.  As shown in Table 4, the greatest decreases were at schools (68% decrease), on commuter routes (41% decrease) and in residential areas (37% decrease).  These were the only locations with statistically significant increases in percent helmet wearing of children (see Table 3.1 of Karkhaneh, 2011), suggesting that the increases in helmet wearing were achieved mainly by discouraging cycling by children who dislike helmets, rather than persuading them to don helmets and continue cycling.  Convincing parents that cycling is so dangerous that every child must wear a helmet at all times may also may also lead to the conclusion that it is safer still not to allow children to cycle at any time.

Table 4.  Comparison of pre and post-law surveys, cyclists aged < 13.  From Karkhaneh, 2011, Table 5-1

 

Pre-law survey (2000)

Post-law survey (2006)

Cyclists per hour Ratio of post-law to pre-law counts1

 

No of Cyclists

Total Hours

Cyclists per hour

No of Cyclists

Total Hours

Cyclists per hour

All cyclists

1175

330.3

3.56

494

313.2

1.58

0.44* (0.36 to 0.55)

Urban

1039

300.0

3.46

409

284.7

1.44

0.41* (0.33 to 0.52)

Non-urban

136

30.3

4.49

85

28.5

2.99

0.66 (0.38 to 1.18)

Site type:
School

854

71.0

12.0

246

63.3

3.89

0.32* (0.24 to 0.44)

Campus/colleges

2

12.0

0.17

8

10.0

0.80

4.80* (1.10 to 20.9)

Park

69

40.0

1.72

75

36.0

2.09

1.21 (0.62 to 2.37)

Cycling path

54

43.6

1.24

48

44.7

1.07

0.87 (0.54 to 1.38)

Commuter route

88

61.7

1.43

53

63.4

0.84

0.59* (0.37 to 0.92)

Residential

108

102.0

1.06

64

95.8

0.67

0.63* (0.41 to 0.98)

Weather:
Wet

147

68.1

2.16

57

60.8

0.94

0.43* (0.26 to 0.73)

Dry

1028

262.2

3.92

437

252.3

1.73

0.44* (0.35 to 0.56)

Temperature:
Low

188

20.7

9.09

23

19.3

1.19

0.13* (0.08 to 0.22)

Moderate

608

162.6

3.74

246

151.8

1.62

0.43* (0.31 to 0.60)

High

379

147.0

2.58

225

142.1

1.58

0.61* (0.45 to 0.83)

1 Ratio of post-law to pre-law counts (95% confidence intervals in brackets)

Surprisingly the published analysis states (page 80) “Since bicycling rates decreased in only two of the five groups of observation sites (schools and commuter routes) among the legislated target age group (<18) post-legislation and simultaneous increases in cycling were observed in other locations, the results of our study refute claims that helmet legislation has a negative effect on cycling exposure.” (Karkhaneh, 2011)

This is an extraordinary assertion that ignores the many surveys where adult and child cyclists categorically stated that helmet legislation was a deterrent to cycling, or that they would cycle more if they did not have to wear a helmet (Robinson, 1996; Robinson, 2006b; Rissel and Wen, 2011).  The Mexico City and Israeli governments repealed helmet laws in order to increase the likelihood of successful public bike hire schemes (BHRF, 1214). The much lower usage of city cycle schemes in Brisbane and Melbourne also seem likely to be a consequence of helmet laws.

In Alberta, there were large overall decreases in children’s cycling, in all weathers and all temperatures (Table 4).  In a few situations, numbers counted were too small to distinguish between random variation and a reduction in cycle use.  However, a lack of a statistically significant difference does not imply there was no effect, simply that the small numbers involved make it impossible to be certain one way or the other.  The only recorded increase in children’s cycling was from 2 to 8 cyclists under the age of 13 on campus/colleges.  This hardly offsets the 56% overall decrease in children’s cycling! 

A few additional youngsters at colleges/campus might reflect a co-operative arrangement allowing children to access college libraries, sporting or computer facilities.  To see a claim in a PhD thesis that this refutes evidence that helmet laws have a negative effect on cycling is extraordinary.

Helmet laws are likely to affect some cyclists more than others.  Cyclists who routinely use helmets, e.g. sporting or racing cyclists, are unlikely to be affected by helmet laws.  No significant reduction would therefore be expected in areas such as parks that were predominantly used by such cyclists.  This would in no way imply that helmet laws do not discourage other forms of cycling. 

The significant increase in post-law cycling of adults (Table 6) should also be noted.  Without the helmet law, there might have been a similar increase in children’s cycling.  Consequently, helmet laws could still be discouraging cycling (and have a significant effect on public health) even if cycling did not decrease, but would have been expected to increase in the absence of helmet legislation.

More importantly, comparisons of post and pre-law injury rates should take account of the reduction in cycling, irrespective of whether such reductions can be attributed to helmet laws.  Helmet laws would be counter-productive if injury rates increased because of risk compensation.  Overall risks must therefore be assessed by comparing number of injuries with the amount of cycling.

If helmets encourage cyclists to ride faster, or drivers to overtake with less care, so that the risk of crashes increased, helmet laws would be counter-productive if this was enough to outweigh any benefits of helmets.  Surprisingly, this was not even considered in the published thesis. 

Table 5.  Comparison of pre and post-law surveys, cyclists aged 13-17.  From Karkhaneh, 2011, Table 5-2

 

Pre-law survey (2000)

Post-law survey (2006)

Cyclists per hour Ratio of post-law to pre-law counts

 

No of Cyclists

Total Hours

Cyclists per hour

No of Cyclists

Total Hours

Cyclists per hour

All cyclists

635

330.3

1.92

440

313.2

1.41

0.73* (0.57 to 0.94)

Urban

560

300.0

1.87

410

284.7

1.44

0.77* (0.60 to 0.99)

Non-urban

75

30.3

2.48

30

28.5

1.05

0.43 (0.18 to 1.01)

Site type:
School

306

71.0

4.31

151

63.3

2.38

0.55 (0.31 to 1.00)

Campus/colleges

9

12.0

0.75

8

10.0

0.80

1.10 (0.59 to 1.93)

Park

46

40.0

1.15

38

36.0

1.06

0.92 (0.54 to 1.56)

Cycling path

83

43.6

1.90

73

44.7

1.63

0.86 (0.59 to 1.25)

Commuter route

101

61.7

1.64

69

63.4

1.09

0.67 (0.43 to 1.04)

Residential

90

102.0

0.88

101

95.8

1.05

1.19 (0.79 to 1.80)

Weather:
Wet

142

68.1

2.08

111

60.8

1.82

0.88 (0.46 to 1.68)

Dry

493

262.2

1.88

329

252.3

1.30

0.69* (0.54 to 0.89)

Temperature:
Low

57

20.7

2.76

5

19.3

0.26

0.09* (0.02 to 0.38)

Moderate

286

162.6

1.76

207

151.8

1.36

0.78 (0.51 to 1.18)

High

292

147.0

1.99

228

142.1

1.60

0.81 (0.61 to 1.08)

In conclusion, when the data are correctly analysed, accounting for the reduction in children’s cycling, the results strongly suggest that child and teenage cyclists in Alberta are more likely to suffer both head and non-head injuries than before helmet laws were introduced.  This is consistent with the latest review of Canadian data showing “In general the rate of head injuries is declining, but this is not consistent across the country, nor is it attributable to legislation as some provinces with legislation experienced a decline while others did not.” (Middaugh-Bonney et al, 2010)

Table 6.  Comparison of pre and post-law surveys, adult cyclists.  From Karkhaneh, 2011, Table 5-3

 

Pre-law survey (2000)

Post-law survey (2006)

Cyclists per hour Ratio of post-law to pre-law counts

 

No of Cyclists

Total Hours

Cyclists per hour

No of Cyclists

Total Hours

Cyclists per hour

All cyclists

2077

330.3

6.29

2375

313.2

7.58

1.21* (1.03 to 1.41)

Urban

2004

300.0

6.68

2335

284.7

8.20

1.23* (1.05 to 1.44)

Non-urban

73

30.3

2.41

40

28.5

1.41

0.58* (0.35 to 0.97)

Site type:
School

124

71.0

1.75

207

63.3

3.27

1.87* (1.17 to 2.99)

Campus/colleges

201

12.0

16.8

248

10.0

24.8

1.48 (0.90 to 2.45)

Park

577

40.0

14.4

524

36.0

14.6

1.01 (0.63 to 1.63)

Cycling path

396

43.6

9.08

425

44.7

9.50

1.05 (0.77 to 1.41)

Commuter route

417

61.7

6.76

505

63.4

7.97

1.18 (0.88 to 1.58)

Residential

362

102.0

3.55

466

95.8

4.86

1.37* (1.06 to 1.78)

Weather:
Wet

327

68.1

4.8

300

60.8

4.93

1.03 (0.63 to 1.68)

Dry

1750

262.2

6.67

2075

252.3

8.22

1.23* (1.04 to 1.46)

Temperature:
Low

35

20.7

1.69

40

19.3

2.07

1.22 (0.64 to 2.34)

Moderate

801

162.6

4.93

790

151.8

5.21

1.06 (0.82 to 1.36)

High

1241

147.0

8.44

1545

142.1

10.9

1.29* (1.05 to 1.58)

References

BHRF, 1055

Head injuries up after Alberta law?. .

BHRF, 1214

Helmet laws repealed or reduced in scope. .

Eureka, 2006

Wearing a helmet puts cyclists at risk, suggests research. ErekAlert!, 11 Sep 2006.

Hagel et al, 2006

Hagel BE, Rizkallah JW, Lamy A, Belton KL, Jhangri GS, Cherry N, Rowe BH, 2006. Bicycle helmet prevalence two years after the introduction of mandatory use legislation for under 18s in Alberta, Canada. Injury Prevention 2006;12:262-265.

Karkhaneh, 2011

Karkhaneh M, 2011. Bicycle helmet use and bicyclists head injuries before and after helmet legislation in Alberta Canada. University of Alberta .

Messiah et al, 2012

Messiah A, Constant A, Contrand B, Felonneau ML, Lagarde E, 2012. Risk compensation: a male phenomenon? Results from a controlled intervention trial promoting helmet use among cyclists. American Journal of Public Health May 2012;102(S2):S204-S206.

Middaugh-Bonney et al, 2010

Middaugh-Bonney T, Pike I, Brussoni M, Piedt S, Macpherson A, 2010. Bicycle-related head injury rate in Canada over the past 10 years. Injury Prevention 2010;16:A228.

Phillips, Fyhri and Sagberg, 2011

Phillips RO, Fyhri A, Sagberg F, 2011. Risk compensation and bicycle helmets. Risk Analysis 2011; Mar 18.

Rissel and Wen, 2011

Rissel C, Wen LM, 2011. The possible effect on frequency of cycling if mandatory bicycle helmet legislation was repealed in Sydney, Australia: a cross sectional survey. Health Promotion Journal of Australia 2011; 22: 178-83.

Robinson, 1996

Robinson DL, 1996. Head injuries and bicycle helmet laws. Accident Analysis & Prevention 1996 Jul;28(4):463-75.

Robinson, 2006b

Robinson DL, 2006. No clear evidence from countries that have enforced the wearing of helmets. BMJ 2006;332:722-725.

Walker, 2007

Walker I, 2007. Drivers overtaking bicyclists: Objective data on the effects of riding position, helmet use, vehicle type and apparent gender. Accident Analysis & Prevention 2007 Mar;39(2):417-25.