What are the brake system requirements under 49 CFR 393.40?

Short answer

The brake system requirements under 49 CFR 393.40 include:

1. Service brakes that meet the applicable requirements

2. Parking brake systems that meet the requirements of 393.41

3. Emergency brakes that meet the requirements of 393.40(e) or FMVSS Nos. 105 and 121

The rule says

"Each commercial motor vehicle must have brakes adequate to stop and hold the vehicle or combination of motor vehicles." (49 CFR 393.40(a))

"Each commercial motor vehicle must meet the applicable service, parking, and emergency brake system requirements provided in this section." (49 CFR 393.40(a))

"Motor vehicles equipped with hydraulic brake systems and manufactured on or after September 2, 1983, must, at a minimum, have a service brake system that meets the requirements of FMVSS No. 105 in effect on the date of manufacture." (49 CFR 393.40(b)(1))

In plain English

The brake system requirements under 49 CFR 393.40 are designed to ensure that commercial motor vehicles can stop and hold safely under any loading conditions. This includes having service brakes, parking brake systems, and emergency brakes that meet specific requirements. For example, vehicles with hydraulic brake systems manufactured after September 2, 1983, must meet the requirements of FMVSS No. 105. Vehicles with air brake systems manufactured after March 1, 1975, must meet the requirements of FMVSS No. 121. Inspectors will check for compliance with these requirements during inspections, and non-compliance can result in fines and out-of-service orders.

What to do

• Ensure that all commercial motor vehicles have brakes adequate to stop and hold the vehicle or combination of vehicles
• Verify that service brakes, parking brake systems, and emergency brakes meet the applicable requirements
• Check the manufacture date of the vehicle to determine which FMVSS requirements apply
• Regularly inspect and maintain brake systems to ensure compliance with 49 CFR 393.40 requirements