Metro's zero tolerance policy on food, trash and other sources of disorder embodies the "broken windows" philosophy of crime reduction. This philosophy also extends to the use of station restroom facilities. A longstanding policy, intended to curb unlawful and unwanted activity, has been to only allow employees to use Metro restrooms. One widely publicized example of this was when a pregnant woman was denied access to the bathroom by a station manager at the station. Metro now allows the use of restrooms by passengers who gain a station manager's permission, except during periods of heightened terror alerts.