The final rule requires ESC systems on heavy trucks and large buses exceeding 26,000 pounds (11,793 kg) in gross weight. Compliance will be tested using a “J-turn” test that replicates a curved highway off-ramp. It will take effect for most heavy trucks two years from publication. The requirement will take effect in three years for buses larger than 33,000 pounds (14,969 kg) and four years for those weighing between 26,000 and 33,000 pounds.
ESC works instantly and automatically to maintain directional control in situations where the driver’s own steering and braking cannot be accomplished quickly enough to prevent the crash. The National Transportation Safety Board has recommended a requirement for ESC on heavy-duty vehicles since 2011. The Moving Ahead for Progress in the 21st Century Act (MAP-21), enacted in 2012, directed NHTSA to consider an ESC requirement for motorcoaches, which are covered in the new rule. A rule requiring light-duty vehicles to include ESC took effect in 2012.
NHTSA estimates the rule will prevent as many as 1,759 crashes, 649 injuries and 49 fatalities each year. ESC will prevent up to 56% of untripped, rollover crashes—i.e., rollover crashes not caused by striking an obstacle or leaving the road.