Background: Promotion of physical activity is a public health priority, and environmental factors influence physical activity behavior. Valid and reliable automated measurement tools of physical activity for assessment and evaluation within public settings are needed. Methods: Searches of the research literature and governmental reports from physical activity, transportation, and recreation fields were conducted to identify methods of automated counting and validation studies. The article provides a summary of (a) current methods and uses of automated counters, (b) information about validity and reliability where available, (c) strengths and limitations of each method, and (d) measurement issues. Results: Existing automated counting technology has strengths and limitations. Infrared sensors have been the most commonly used type of monitor and can mark date and time of passage, but are vulnerable to errors due to environmental conditions; cannot detect more than one person passing at a time; cannot identify mode of activity or distinguish among individuals; and lack consistent and adequate reliability for use in open spaces. Seismic devices and inductive loops may be useful for specific applications. More information is needed concerning the validity and reliability of infrared sensors, seismic devices, and inductive loops for confined areas. Computer imaging systems hold potential to address some of the limitations of other automated counters and for applications in both confined and open areas, but validation research is in the initial stages. Conclusions: Although automated monitoring is a promising method for measurement of physical activity, more research is necessary to determine the acceptable parameters of performance for each type of automated monitor and for which applications each is best suited.
