Detection of spatially clustered outbreaks in motor vehicle crashes: What’s the best method?

Spatio-temporal surveillance methods for detecting outbreaks of disease are fairly common in the literature, with the SCAN statistic setting the benchmark. Spatio-temporal surveillance methods are less commonly described in relation to detection of outbreaks in motor vehicle crashes. The exponential two-pass CUSUM (E2PC) plan designed to detect age-clustered outbreaks is here compared to the SCAN statistic for early detection of spatially clustered outbreaks in crashes. If the shape and size of the outbreaks are known in advance, then the SCAN statistic has advantages over the E2PC plan. However, if outbreaks vary significantly in terms of size but are roughly rectangular in shape then the E2PC plan as outlined in this paper has advantages over the SCAN statistic.