Using funnel plots in public health surveillance

<p>Abstract</p> <p>Background</p> <p>Public health surveillance is often concerned with the analysis of health outcomes over small areas. Funnel plots have been proposed as a useful tool for assessing and visualizing surveillance data, but their full utility has not been appreciated (for example, in the incorporation and interpretation of risk factors).</p> <p>Methods</p> <p>We investigate a way to simultaneously focus funnel plot analyses on direct policy implications while visually incorporating model fit and the effects of risk factors. Health survey data representing modifiable and nonmodifiable risk factors are used in an analysis of 2007 small area motor vehicle mortality rates in Alberta, Canada.</p> <p>Results</p> <p>Small area variations in motor vehicle mortality in Alberta were well explained by the suite of modifiable and nonmodifiable risk factors. Funnel plots of raw rates and of risk adjusted rates lead to different conclusions; the analysis process highlights opportunities for intervention as risk factors are incorporated into the model. Maps based on funnel plot methods identify areas worthy of further investigation.</p> <p>Conclusions</p> <p>Funnel plots provide a useful tool to explore small area data and to routinely incorporate covariate relationships in surveillance analyses. The exploratory process has at each step a direct and useful policy-related result. Dealing thoughtfully with statistical overdispersion is a cornerstone to fully understanding funnel plots.</p

Do speed cameras produce net benefits? Evidence from British Columbia, Canada

Traffic collisions kill about 43,000 Americans a year. Worldwide, road traffic injuries are the leading cause of death by injury and the ninth leading cause of all deaths. Photo Radar speed enforcement has been implemented in the United States and many other industrialized countries, yet its cost-effectiveness from a societal viewpoint, taking all significant impacts into account, has not been reported. This paper fills this gap, reporting on a Photo Radar traffic safety program introduced in 1996 in British Columbia, Canada, and incorporating the results of rigorous statistical analyses on speed and crash impacts into a comprehensive cost-benefit analysis from both societal and sponsoring-agency perspectives. The study reveals that the Rhoto Radar Program cost C$27 million per year in 2001 Canadian dollars (?US$21 million) and generated benefits valued at $142 million per year (?US$109 million), for net societal benefits of C$115 million per year (?US$88 million). It was estimated that the sponsoring agency saved C$38 million (?US$29 million) annually in claim costs. These results are robust to plausible alternate assumptions. Societal net benefits become negative only if the reduction in injuries and fatalities is one standard error below the expected value, or if private travel time is valued at or above C$15 per hour. Agency claim cost savings are greater than program costs under all scenarios tested. These results are likely applicable to jurisdictions in developed countries with similar traffic infrastructure: Greater use of highway photo radar speed enforcement would be good public policy. © 2006 by the Association for Public Policy Analysis and Management