In this proposal, we seek to address conclusively two knowledge gaps: 1) the lack of data on the relationship between PGY2+ (post graduate year 2) sleep deprivation and patient safety; and 2) the lack of data on the relationship between resident sleep deprivation and preventable patient injuries. Through the Clinical and Translational Science Award (CTSA)-funded Sleep Research Network, the largest and only federally-funded sleep science network in the U.S., we propose conducting a multi-center randomized crossover trial in six pediatric ICUs staffed by PGY2 and PGY3 residents. We will compare rates of all serious errors (i.e., rates of harmful and other serious medical errors due to any cause, including but not limited to fatigue-related errors, handoff errors, and provider knowledge deficits) of a sleep and circadian science-based (SCS) intervention schedule with a traditional schedule that includes frequent shifts of 24 hours or longer. Our specific aims will be: