Who decides how many hours we're allowed to work, driving trucks, fixing jet engines, taking care of children, or doing anything else? Our and our employer's l

Who decides how many hours we're allowed to work, driving trucks, fixing jet engines, taking care of children, or doing anything else? Our and our employer's liability for errors is enough motivation to maintain safety at a reasonable level. Put another way, is there statistical evidence of the efficacy of these regulations in reducing trucking accidents? Not that I could find!