Preventing child pedestrian injury: pedestrian education or traffic calming? Ian Roberts I~ljuly Prtvention Research Centre, C'niversity of Auckland

Toni Ashton Department of Community Health, University of Auckland

Roger Dunn

Trevor Lee-Joe

Department of Engineering, University of Auckland

Prevention Research Centre, University of Auckland I n j u y

Abstract: The traditional approach to the prevention of child pedestrian injuries in New Zealand is pedestrian education. However, none of the programs currently being implemented in New Zealand have ever been shown to reduce injury rates. The allocation of scarce resources to pedestrian education must therefore be questioned. In this paper we estimate the number of serious child pedestrian injuries which might be prevented if the resources allocated to pedestrian education were allocated instead to environmental approaches, in particular, to traffic calming. It is estimated that approximately 18 hospitalisations of child pedestrians could be prevented each year under this alternative resource allocation, disregarding any other benefits of traffic calming. These results emphasise the need to consider the potential sacrifices involved in the allocation of scarce resources to child pedestrian education. (AustJ Public Health 1994; 18: 209-12)

edestrian-motor-vehicle collisions are a lead- ing cause of death and serious injury in P chilcIhood.I.' Each year in New Zealand an

average of thirty children are killed and over four hundred children are admitted to hospital as a result of pedestrian injuries.' Internationally, two distinct approaches to the prevention of child pedestrian injuries can be distinguished.5 In Britain and New Zealand, the mainstay of preventive strategy has com- prised efforts to improve child pedestrian behaviour through pedestrian education programs. However, none of the programs currently being implemented have ever been shown to reduce injury rates. In the Scandinavian countries, greater emphasis has been given to modification of the urban traffic environ- ment. For example, in Denmark, a major commit- ment has been made to reducing vehicle speeds in residential areas using traffic calming methods such as speed humps." There is substantial evidence sup- porting the efficacy of environmental approaches to prevention, which is not the case for pedestrian

Regardless of the approach, the prevention of child pedestrian injuries involves the use of scarce resources. The purpose of this case study is to draw attention to the consequences of allocating scarce resources to road safety education by estimating the benefits forgone in not allocating those resources to traffic calming.

- Correspondence t o Dr Ian Roberts, Injury Prevention Research Centre, Department of Community Health, Univenity of Aurk- land, Private Bag 92019. Auckland. New Zealand. Fax 9 373 7503.

Methods The costs associated with the central provision of child pedestrian education in New Zealand were identified, measured and valued. Items were included as costs if they entailed an opportunity cost as a result of being used in a prevention program. The cost of implementing traffic calming in an aver- age residential street was then calculated. Next, the number of streets in which traffic calming could be implemented for the same amount of resources as was used in the provision of pedestrian education was estimated. Finally, the number of serious pedestrian injuries which might be prevented under this alterna- tive resource allocation was estimated. This calcu- lation was based on an estimate of the surface area (and child population) over which traffic calming could be implemented, published estimates of the proportion of pedestrian injuries which occurred on streets where traffic calming was feasible and data on the efficacy of traffic In order to simplify the analysis, only benefits accruing in the base year were considered.

Costs: child pedestrian education The program costs of child pedestrian education were obtained from the National Road Safety Plan database.!' Only programs aimed predominantly at improving the safety of children as pedestrians were counted. Centrally provided road safety education (national child road safety education) takes place in schools and therefore displaces other educational input from the curriculum. The police output target for the provision of road safety education in 1993 was a total of 61 020 police hours of education."'

AUSTRALIAN JOURNAL OF PUBLIC HEALTH 1994 VOL 18 NO 2 209

ROBERTS E T AL

Assuming the target number of hours were to be achieved, the value of the educational input forgone was estimated by multiplying hours of teaching time forgone by the hourly (class contact) primary teacher's wage. All values were inflation adjusted, on the basis of the consumer price index, to 1993, the base year for cost valuation. The costs of the pro- grams are shown in Table 1 .

Costs: traflic calming The costs associated with the provision of traffic calming for an average residential street are pre- sented in Table 2. Quotations of the costs associated with traffic surveys, planning and design were obtained from private engineering consultancies. Prior to implementing traffic calming, councils con- sult with residents, usually by questionnaire. Esti- mates of the costs of consultation were obtained from Auckland City Council area offices. Traffic calming is constructed by private engineering firms operating in a competitive market in contractual arrangements with city councils. It is assumed that market prices reflect the true social value of these resources. Construction costs were obtained by asking each of the four mainland Auckland City Council area offices the price they would expect to pay for traffic calming for an average residential street. Three area offices estimated a price of $10 000, one a price of $12 000. These prices included the price of additional road signs and any upgrading of street lighting. An average of the four estimates was used in the analysis.

The increased time spent travelling as a result of the speed reductions was estimated for a residential street 0.5 km long for which average speed falls by 1 1 km/h from 47 km/h (increased travel time per vehicle multiplied by the median number of vehicles per day and the number of days in the year, adjusted for diversion factor).ti Data on the median number of vehicles per day for a residential street (750 vehicles per day) were obtained from the Auckland Child Ped- estrian Injury Study (I. Roberts, unpublished data). Overseas studies have demonstrated that following traffic calming there is a reduction in traffic volume of up to 30 per cent as vehicles take alternative routes.' Theoretically, since these routes are only marginally longer, the additional travel time for diverted vehicles can be ignored. For the purpose of

Table 2: Costs of traffic calming in an average residential street

k t i v i t y Cost ($NZ) Direct costs Traffic surveys and planning Designs Consultation with residents Labour, capital, natural resourceso Total direct costs

1 500 1 000

300 10 500 13 300

Indirect cosfs Increased travel time (1 5% diversion) 11 586 Estimated 5% increase in fuel consumption 700 Total indirect costs 12 286 Estimated cost of traffic calming 25 586

Note: (a) Includes signs, street lighting

this analysis a 15 per cent diversion was assumed. The increased travel time was priced on the basis of the average hourly wage of $14.93." It has been esti- mated that at the reduced speed there would be a 5 per cent increase in fuel consumption (New Zealand Automobile Association, personal communication).

Estimated number of pedestrian injuries prevented On the basis of the preceding estimates it can be cal- culated that for the resources used to provide ped- estrian education, traffic calming could be implemented in 248 residential streets. If traffic calming were implemented rationally it would be aimed at those areas with the highest child pedestrian injury rates (Table 3). The data in Table 3 are for the six-year period 1982-1 987. Injuries were averaged over six years to reduce the effect of random variability.

The number of residential streets amenable to traffic calming for each of the census area units is shown in Table 3. These estimates were obtained from detailed maps of the Auckland regon. On the basis of 248 residential streets, census areas 1 t o 12 and 50 per cent of census area 13 could be traffic calmed. The corresponding number of injuries (31.2), when multiplied by the proportion of child

Table 3: Census area units ranked by rates of hospitalisation due t o child pedestrian injury

Table 1 : Costs of child pedestrian education Rate/100 000 No. Ronk Census ore0 N u Population years streets

Program

Direct costs National child road safety education Road safety drama (Christchurch City Council) School travel project (Christchurch City Council) Road safety education directory 'Keeping ourselves safe' Total program costs, 1991 Total program costs, 1993" Indirect costs Educational input forgoneb

Estimated cost of road safety education

Cost ($NZ)

4 663 700 10 000 4 000

1 1 875 150 000

4 839 575 4 950 731

1 403 460 6 354 191

Notes: (a) (b) 61 020 hours at $23.00 per hour.

1991 costs adiusted by the consumer price index of 115811 132.

1 Otahuhu East 2.7 1339 201.6 2 Mt Wellington 1.5 82 1 182.7 3 Otara West 3.2 1787 179.1 4 Te Pop0 1 .O 596 167.8 5 Otora South 4.5 2792 161.2 6 Ellerslie 1.5 1074 139.7 7 Mangere East 3.7 2987 123.9 8 Favona 1.8 1451 124.1 9 Otoro North 2.5 2233 112.0 10 Mangere Bridge 2.0 1812 110.4 11 Flat Bush 4.0 3771 106.1 12 Ponrnure 1 .o 1109 90.2 13 Hariono 3.5 4122 84.9

15 Grey Lynn West 3.0 4313 69.6 14 Popotoe Central 0.8 1054 79.1

Note- (a) N=six-year average number of iniuries

17 44 18 11 13 21 29

7 17 28 6

23 27 24 40

210 AUSTRALIAN JOURNAL OF PUBLIC HEALTH 1994 VOL 18 NO 2

CHILD PEDESTRIAN INJURY

pedestrian injuries occurring on residential streets (0.75)," estimates the number of injuries potentially preventable by traffic calming.

For interventions which cannot be implemented at the individual level, such as traffic calming, the counterpart of the randomised controlled trial is the controlled community intervention trial.I3 A control group is mandatory, since befwe and ajer compari- sons might be confounded by changes in the back- ground rate." The efficacy estimate used in this study was taken from a large-scale controlled community intervention trial of speed humps conducted in

A particular advantage of this trial was that 95 per cent confidence intervals (CI) were pre- sented (78 per cent reduction in serious injury, CI 26 to 93), providing a suitable range of values for sensi- tivity analysis.

Using this efficacy estimate i t can be calculated that 18 (CI 6 t o 22) pedestrian injury hospitalisations might be prevented in the base year. If the pro- portion of pedestrian injuries on streets amenable t o traffic calming were only 0.5 then 12 (CI 4 to 15) injuries might be prevented. If instead of a 15 per cent traffic diversion, there were a 30 per cent traffic diversion following traffic calming, the travel time cost would fall to $9 540. In this case, 270 residential streets might receive traffic calming. On this basis, 19 injuries (CI 6 to 23) might be prevented. Finally, since it could be argued that the valuation of edu- cational input forgone on the basis of the hourly teacher's wage overstates the opportunity cost of children's time, the analysis can be repeated exclud- ing this cost. O n this basis, an estimated 193 residen- tial streets could be traffic calmed and 14 (CI 5 t o 16) injuries might be prevented.

Discussion Pedestrian education is the traditional approach t o the prevention o f child pedestrian injuries in N e w Zealand. However, none of the current programs has ever been shown to reduce injury rates. The inter- national literature is replete with examples of ineffec- tive child pedestrian education programs. Since centrally provided road safety education is likely t o he additional to that provided by parents, the mar- ginal benefit of centrally provided education may he minimal and hence difficult to detect.15 Indeed, in the absence o f efficacy data it is often assumed that road safety education is minimally effective. Even this assumption may be unwarranted. If the knowl- edge that children have received road safety edu- cation gives parents unrealistic expectations of children's performance in traffic, this might result in increased traffic exposure and increased injury rates. Analogously, driver education in United States schools was found to increase irijury rates because driving licensure among 16- and 17-year-olds was increased. It has been estimated by willingness-to-pay estimates that the elimination of driver education would save approximately US $2.2 billion."

Every choice involves a sacrifice. This idea is underscored in the economists' concept of oppor- tunity costs. If resources are allocated to pedestrian education programs, those resources become unavailable for other uses. Opportunity cost refers to the value of the sacrifice, (the benefits forgone)

because the resources are not available for their best alternative use. The aim of this study was to examine the opportunity cost of road safety education by esti- mating the benefits forgone in not allocating those resources to traffic calming. In doing so, several assumptions were made, in particular, the assump- tion that traffic calming is the best alternative resource use. I t is possible that public policy changes which reduce traffic volumes by strengthening the public transport system may prove more cost- effective." However, only for traffic calming were published efficacy data from large-scale community intervention trials available. For the purposes o f this study, the benefits of traffic calming were estimated on the basis o f high-risk areas in Auckland. In prac- tice, it is unlikely that this would be politically accept- able. I t would also have been possible to rank pedestrian injury rates for all New Zealand and allo- cate resources accordingly or else to partition avail- able resources on a regional basis.

The efficacy estimate used in this study was chosen because of the large scale of the study, because a con- trol group was used and because confidence intervals were presented along with the point estimate. Since traffic calming diverts traffic onto other streets, there may be an increase in casualties on these streets, in which case the estimate used in this study may be an overestimate. It is also possible that the estimate used may not be applicable in an Australasian context, although in a review of nine- teen studies of casualty reductions following traffic calming, efficacy estimates of a similar magnitude t o the one used in this study were found."' While the val- idity and applicability of any single efficacy estimate is open to question, arguably the most important con- sideration is that there are studies that have consist- ently shown a beneficial effect of traffic calming. This cannot be claimed for child pedestrian education programs.

A major component of the costs of traffic calming is the increased travel time resulting from speed reductions. This time is readily estimated and valued. Much more difficult to estimate is the value o f the time loss averted by parents as a result of traffic calni- ing. It has been estimated that in Britain approxi- mately I 356 million hours are spent each year escorting children, principally because of traffic danger.Iq It is possible that improving safety in resi- dential areas would reduce this time. The inability to estimate and value escorting time in this study would underestimate the cost-effectiveness o f traffic calming.

Implicit in this study is that the prevention of child pedestrian injuries is the only benefit accruing from the prevention strategies examined. For child ped- estrian education there may be some additional intangible benefits such as greater police liaison with the community. However, in the case of traffic calni- ing there are other tangible benefits. Evaluation studies have demonstrated reduction in injuries fol- lowing traffic calming for all road users, including cyclists, adult pedestrians and motor vehicle occupanls."' The results of this study suggest that t o be as cost-effective as traffic calming, pedestrian edu- cation must prevent at least 18 hospitalisations due t o child pedestrian injury per year, without considering any other benefits of traffic calming.

AUSTRALIAN JOURNAL OF PUBLIC HEALTH 1994 VOI I8 NO 2 21 I

PETERSEN

Cost-effectiveness is only one criterion for choice. The way the benefits of preventive programs are dis- tributed in society is also an important criterion.2’ Current police performance targets are that 70 per cent of all schools receive at least one visit from a road safety officer each year. If all children were at equal risk of pedestrian injury this would amount to an equitable distribution of the anticipated benefits. However, both New Zealand and overseas studies clearly indicate that this is not so. A geographic analy- sis of child pedestrian injury in Auckland demon- strated discrete areas of increased incidence. Injury rates are strongly correlated with census area unem- ployment, a proxy for socioeconomic disadvantage. Pedestrian injury admission rates to intensive care facilities in Auckland are over three times higher for Maori and Pacific Island children than for children of European origin.” An equitable distribution of ben- efits would involve allocating resources to areas where need is greatest. Traffic calming is easier to allocate on the basis of need than pedestrian edu- cation, which is part of the national curriculum.

In the absence of data to support its efficacy, locat- ing road safety education at the forefront of child pedestrian injury prevention strategy amounts to an act of faith. The results of this study highlight the sac- rifice that this may entail.

References 1 . Rivara FP. Child pedestrian injuries in the United Slates. Am

J Drr Child 1990; 144: 692-6. 2. Roberts I, Norton R. Hassall I. Child pedestrian injury 1978-

87. NZ Med J 1992; 105: 51-2. 3. Roberts I. International trends in pedestrian injury mor-

tality. Arch Dis Child 1993; 68: 190-2. 4. Kjemtrup K. Herrstedt L. Speed management and traffic

calming in Europe: a historical view. Accid Anal Prm 1992; 24: 57-65.

5.

6.

7.

8.

9.

10.

11.

12.

13.

Faure A, Neuville A. Safety in urban areas: the French pro- gram ‘Safer city, accident-free districts’. Accid Anal P r w 1992; 24: 39-44. Engel U, Thomsen L. Safety effects o f speed reducing measures in Danish residential areas. Accid Am1 Preu 1992;

Vis AA, Dijkstra A. Safety effects of 30 km/h zones in the Netherlands. Accid Am1 Prm 1992; 24: 75-86. Roberts I, Norton R, Dunn R, Hassall I , Leeljoe T. Environ- mental factors and child pedestrian injuries. Aust J Public Health 1994; 18: 43-6. Nation01 road safety plan. Wellington: Officials’ Committee on Road Safety, 199 1 . Safety administratim programme. Wellington: Ministry o f Transport, 1992 Hot off the press: quarterly employment sumvqr (mid-February) 1993. Wellington: Department of Statistics, 1993. Roberts I, Marshall R. Norton R, Borman B. An area analysis of child injury morbidity in Auckland. J Paediatr Child Health 1992; 28: 438-41. Rothman K1. Modprn epidemiolom. Boston: Little, Brown,

24: 17-28.

-_ 1986. Roberts I. Why have child pedestrian death rates fallen? RMJ 1993; 306: 1737-9. Pless IB, Arsenault 1,. The role of health education in the pre- vention of injuries to children. J Soc Issues 1987; 43:

Shiell A, Smith R. A tentative cost-utility analysis of road safety education. Aust J Public Health 1993; 17: 128-30. Rice DP, MacKenzie EJ, et al. Cost ofinju9 in the United Sfafesr a reporl to congress in 1989. San Francisco: Institute for Health and Aging, University of California and Injury Prevention Centre, Johns Hopkins University, 1989. Roberts I, Marshall R, Norton R. Child pedestrian mortality and traffic volume in New Zealand. BMJ 1992; 305: 283. Hillman M, Adams J. Whitelegg J. Oru false move: a study of children’s i.depmdn3 mobilify. London: Policy Studies Insti- tute, 1991.

20. Preston B. Cutting pedestrian casualties: cost-eflectiue ways to mate walking safer. London: Greenprint, 1992.

2 1 . Cohen DR, Henderson JB. Health, prevention and e c m i c s . Oxford Oxford University Press, 1988.

22. Roberts I, Streat S, Judson J, Norton R. Critical injuries in paediatric pedestrians. NZ Med J 1991; 104: 247-8.

4.

5.

87-103. 6.

17.

18.

19.

CORRECTION

Tobacco in Western Australia: patterns of smoking among adults from 1974 to 1991 This article, from the December 1993 issue of the Journal, contained the following statement:

Between 1987 and 1991 the prevalence of smoking among women in the 20- to 24-year age group decreased from 41.2 per cent to 29.0 per cent. This is at odds with findings from the data collected by the Anti Cancer Council of Victoria which indicate that, in 1989. the prevalence of smoking among Aus- tralian women aged 20 to 24 years was 37.7 per cent, which was higher than the prevalence in any other male or female age group. ‘

The Anti Cancer Council authors have pointed out that in the paper published in the Medical J o u m l of .4wtraZia, the highest prevalence was actually in males aged 20 to 24 (41.0 per cent) (p. 798).‘ References

1. Macfarlane JE, Jamrozik K. Tobacco in Western Australia: patterns of smoking among adults from 1974 to 1991. A w t J Public Health 1993; 17: 350-8. Hill DJ, White VM, Gray NJ. Australian patterns of tobacco smoking in 1989. Med J Auct 1991 ; 154: 797-80 1.

2.

21 2 AUSTRALIAN JOURNAL OF PUBLIC HEALTH 1994 VOL. 18 NO 2