On August 12, 2011, the Federal Railroad Administration (FRA) issued a final rule to establish hours of service limitations on train employees of commuter and intercity rail providers. The rule becomes effective on October 15, 2011. This is the first time requirements specifically limiting work hours and mandating minimum rest periods for passenger rail employees have been issued. Previous hours of service requirements applied to both freight and passenger rail employees. Additionally, the new rule introduces a requirement that railroads apply fatigue science to model the risk of fatigue for employees working schedules that include certain night time hours. The new rule permits employees to work up to 12 consecutive hours on duty, or 12 nonconsecutive hours within a 24 hour period if such hours on duty are broken by at least 4 consecutive hours off duty. Off duty-periods vary from 8 to 48 hours depending on the length and times of day of duty time preceding the rest period. The new rule distinguishes between duty tours during hours where the risk of fatigue is deemed to be low, and hours (generally after 8 p.m. and before 4 a.m.) where an elevated risk of fatigue must be mitigated. In order to mitigate the risk of fatigue during night time duty hours, railroads must use biomathematical performance and fatigue models to analyze the risk, implement fatigue mitigation plans on the basis of the completed models, and train employees in fatigue mitigation. Generally, railroads must submit their work schedules and fatigue mitigation regimes for approval by FRA by April 12, 2012. The new rule also applies to train employees engaged in tourist, scenic, historic, and excursion rail transportation.