Several estimation tools were derived to determine ED overcrowding status using various operational parameters such as, but not limited to, total number of ED patients, total ED admission holds, nursing staff, and patient injury severity. However, these tools cannot precisely evaluate ED overcrowding status, nor show strong correlations with ED operational inefficiency. The National Emergency Department Overcrowding Study (NEDOCS) is a widely used estimation tool to determine ED overcrowding status with relatively high consistency rates. However, the study was not able to evaluate interrater reliability since no standard definition of overcrowding existed.