1. #06a - Safety Rules - Rule 81.2.2 - Your personal safety and your responsibility to work safely depends on maintaining a safe distance from equipment. Never cross or step foul of tracks closely in front of or behind moving equipment or close to the end of equipment. In addition, never:

Go between standing equipment if the opening is less than 50 feet or, cross in front of or behind equipment unless there is at least 20 feet between the employee and the equipment.
Go between equipment if the opening is less than 40 feet or, cross in front of or behind moving equipment unless there is at least 20 feet of clearance.