 This research paper examined the reliability and validity of automated active infrared counters as a means of measuring football in urban parks. It found that at least four weeks of data collection was necessary to produce reliable estimates of football, and that infrared counters tended to underestimate football by up to 13.7%. The authors also noted that the number of groups present during an observation period was a significant factor in explaining the differences between infrared and manual counts. This article was offered by DJ Ryan and J S Benton.