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RESEARCH AND PRACTICE: June M. Tester, George W. Rutherford, Zachary Wald, and Mary W. Rutherford A Matched Case–Control Study Evaluating the Effectiveness of Speed Humps in Reducing Child Pedestrian Injuries Am J Public Health 2004; 94: 646-650 [Abstract] [Full text] [PDF]

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Electronic letters published:

Data does not support results claimed by study

Kathleen Calongne, Center for the American Dream, Golden, Colorado   (6 July 2004)

Evaluating speed humps is not that simple

Deborah J Hogan   (6 July 2004)

Speed Humps Do Reduce Hazard for Children

Rebecca Gillman   (19 April 2004)

Data does not support results claimed by study 6 July 2004
Kathleen Calongne, Self-employed The Independence Institute, Center for the American Dream, Golden, Colorado Send letter to journal: Re: Data does not support results claimed by study CalongneK{at}aol.com Kathleen Calongne, et al.	There are a number of problems associated with this study. First, the control group of 100 out of over two hundred children brought to an emergency room for injuries was selected by the authors themselves, rather than on a double blind basis, where the selectors would be independent of the study. Second, it is not stated whether the authors made an attempt to determine if any of the children reportedly injured by cars lived on the 80 streets that had humps built on Oakland streets the two years prior to the 1995 to 2000 data of speed hump locations used by the researchers. Third, even simple percentage calculations of the data seem to be incorrect. There were 100 case patients and 200 controls. Of the tiny sample size of 14 neighborhood injuries, 14 of 100 is stated to be 14%. Six index street injuries should then mean 6 percent. However Table 2 says 6 injuries are 12%. With 200 controls, 46 neighborhood cases equal 23%, but 24 index street cases should be 12%, not 24% as stated. The researchers conclude that speed humps were associated with a 53 percent to 60 percent reduction in the odds of injury or death among children struck by an automobile. However, within a 95 percent confidence interval the odds of an injury on a street without speed humps is found to range from 24 to 95 percent, while the odds on a street with humps has a range of 15 to 106 percent. This is a huge overlap. In fact, it is a 100 percent overlap, meaning that there is no statistical significance to the results. The researchers’ inability to calculate simple percentages seems to explain their failure to recognize the statistical insignificance of their results. Kathleen Calongne
Evaluating speed humps is not that simple 6 July 2004
Deborah J Hogan, traffic safety coordinator City of Bend Send letter to journal: Re: Evaluating speed humps is not that simple dhogan{at}ci.bend.or.us Deborah J Hogan	As much as we would all like to believe that a simple and inexpensive device like a speed hump can reduce pedestrian injury, it just doesn't work that way. While it is true that most children under the age of ten are injured in their neighborhoods, and dart-out crashes describe the most common pedestrian injury, does the speed hump provide overall improved safety for the children in the community? A 15 cm speed hump will cause most vehicles to slow to 15 mph or less, lower than the speed limit for residential streets and probably a speed drivers perceive as inconvenient. So the hump of that height does a couple of things: It diverts traffic to other neighbhorhood streets or collectors that do not have speed humps and it creates a barrier for ambulances and fire engines that will not cross a bump that high. If designated emergency service routes are in place, the second issue can somewhat be addressed, but the traffic diversion effect is unavoidable. If that is the goal, we can dead end all the residential streets and not allow through traffic at all. It is not enough to look at whether safety was improved on the streets where the speed humps were installed, in order to evaluate whether safety was improved, one must evaluate the overall safety benefit to the transportation system. If by installing speed humps on streets A, B, and C we pushed more traffic on to street D, I would expect a higher number of accidents on street D. This would be particularly true of an increase in Dart Out type pedestrian accidents, because the greater the traffic volume, the more likely this type of crash is. We at the City of Bend are very interested in improving safety for pedestrians, children in particular. In order to accurately assess what results in fewer pedestrian injuries, more factors need to be included in the research such as traffic volume, sight distance, availability of alternate routes, presence of sidewalks and on-street parking, etc. This is not a simple analysis. To draw such a conclusion based on incomplete research distracts the public from the truth and focuses "safety" efforts on a quick fix that may not be a fix at all. I know this because when the public calls us with their safety requests, they very often are convinced that a speed hump is the solution, even before the problem has been identified. Then I have to reeducate before I can even begin to address the safety issues.
Speed Humps Do Reduce Hazard for Children 19 April 2004
Rebecca Gillman, Traffic Engineer Send letter to journal: Re: Speed Humps Do Reduce Hazard for Children RGillman{at}nelsonpope.com Rebecca Gillman	Hello, I wholeheartedly agree with the main result of your paper regarding speed humps and child-pedestrian safety. But how exactly does pedestrian safety have to do with "ethnicity" ? Of all the hocus pocus that must be the most ridiculous, in my experience as a traffic engineer.