According to NFPA 1901, the parking brake is required to hold the apparatus on at least what grade percentage?

The requirement for the parking brake to hold the apparatus on a grade is set at 20% as specified in NFPA 1901. This standard ensures that fire service vehicles, which are often heavy and can be difficult to maneuver, have a reliable braking mechanism that can securely hold the vehicle stationary on an incline. A 20% grade translates to a significant slope, which reflects the challenging conditions that vehicles may encounter when responding to emergencies. This specification promotes safety for the crew and prevents accidents that could occur if the vehicle were to roll while parked on an incline. The standard is designed with the understanding that fire service vehicles need to operate effectively in a variety of challenging environments, ensuring that they remain stationary to prevent any unintended movement while firefighters do their critical work.