Jarahi et al. BMC Public Health 2011, 11:281 http://www.biomedcentral.com/1471-2458/11/281 Moreover, there are differences between community and governmental perspectives in WTP for preventive interventions in comparison with curative programs. For instance, in the USA, the reported WTP for care was three times higher than WTP for preventive interven- tion regarding one output [22]. This fact can be accounted as a limitation in comparison of our results with findings of published papers on WTP for services of non-preventive nature. On the other hand, published papers using WTP methods in the field of injury pre- vention are rare; except for two published papers on WTP on car crash protection [23], pedestrians’ safety [8] and one on child safety seats[18]. In studying willingness to pay, payment cards are fre- quently used for contingent valuation, in which the respondents select their choice from cards or options ranging from zero to a pre-determined value [24-26]. In our study we used the multiple choice method instead of payment cards, as in the pilot study, it seemed to be more understandable and acceptable to our respondents. Previous studies comparing dichotomous choice and payment card approaches have identified no evidence of range bias or mid-point bias [26]. Nevertheless, multiple choice questions might not be the best method for eli- citing WTP. Other methods like conjoint analysis or dis- crete choice modeling have been introduced [27]. Further research is necessary to demonstrate if feasibility of application, justifies its general application instead of payment card. One of the difficulties with CVM studies is making the scenario realistic to the respondent [11]. For this pur- pose, the questionnaire of this research was only offered to parents who had a car in their family. In addition, they were provided with short information on the toll of road traffic deaths among pediatric car passengers in Iran and a pictorial introduction about CSS. This inclu- sion criterion could potentially limit the generalizability of our findings as car-owned families might be of higher economic status and thus have higher WTP. Despite this fact, more than 80 percent of these families were in low-middle income groups, minimizing the real poten- tial for this bias. Conclusion The main finding of this research was low level of par- ental willingness to pay for child car safety seats against moderate to high perceived efficacy. The main predictor for willingness to pay was family income level. A consid- erable unmet need was also observed regarding CSS advice from the physician responsible for the care of the child/family. This research can also be of practical importance for health policy makers to initiate CSS insurance coverage or lending programs parallel to deci- sions for obligatory CSS regulations. Future research Page 5 of 6 can examine the effectiveness and feasibility of methods suggested in the paper to promote CSS use in Iran. Acknowledgements This study was based on a research grant (No. 81) from Sina Trauma Research Center, Tehran University of Medical Sciences. Author details 1Department of Community Medicine, Mashad University of Medical Sciences, Mashad, Iran. 2Sina Trauma Research Center, Tehran University of Medical Sciences, Tehran, Iran. 3Department of Community Medicine, Tehran University of Medical Sciences, Tehran, Iran. 4Department of Health Management and Economics, School of Public Health/Knowledge Utilization Research Center, Tehran University of Medical Sciences, Tehran, Iran. Authors’ contributions MK proposed the idea of this research and participated in the proposal development, data analysis, interpretation and development of the manuscript. LJ participated in the proposal development, data collection and analysis, interpretation and development of the manuscript. AR participated in the proposal development, interpretation of willingness to pay findings and development of the manuscript. All authors have read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 30 June 2010 Accepted: 8 May 2011 Published: 8 May 2011 References 1. Rasouli MR, Nouri M, Zarei MR, Saadat S, Rahimi Movaghar V: Comparison of road traffic fatalities and injuries in Iran with other countries. Chinese J of Traumatology 2008, 11(3):131-134. 2. 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