The NTSB also cited runway incursions, which have been cited every year since the lists inception in 1990. "These incidents continue to occur with alarming frequency," the NTSB said. "The FAA indicates that during fiscal year 2005 there were 327 incursions, and during 2006 there were 330. A system introduced by the FAA provides warning to air traffic controllers, but not to the flight crews, a fact that severely reduces the amount of time that pilots have to react to an impending incursion." The NTSB wants the FAA to implement a safety system that would provide direct warning to flight crews. Also among the board's concerns were pilot fatigue and icing. Rest rules for pilots and mechanics are "archaic" in many cases, the board said. The FAA should establish scientifically based regulations that set limits on hours of service, provide predictable work and rest schedules, and consider human sleep and rest requirements. The FAA also needs to conduct more research on aircraft structural icing and revise its criteria for icing certification and its rules for operating in icing conditions, the NTSB said.