This is an ongoing, long term VRTC-based research program aimed at improving the safety performance of heavy trucks. In the past, research for this program has primarily focused on braking issues, but has also included research in other heavy truck safety areas such as fuel line crossover structural integrity, tires, handling and rollover.
- NHTSA Report: Tractor Semitrailer Stability Objective Performance Test Research - Yaw Stability, DOT HS 811 734, May 2013
- NHTSA Report: Class 8 Mack Straight Truck Emulating a Refuse Hauler –Braking Improvement Study, DOT HS 811 747 May 2013
- NHTSA Report: Test Track Lateral Stability Performance of Motorcoaches Equipped with Electronic Stability Control Systems, DOT HS 811 633, April 2013
- NHTSA Report: Tractor Semi-Trailer Stability Objective Performance Test Research - Roll Stability DOT HS 811 467, May 2011 [PDF]
- NHTSA REPORT: Study of Heavy Truck S-Cam, Enhanced S-Cam, and Air Disc Brake Models Using NADS DOT HS 811 367, October 2010 [PDF]
- NHTSA REPORT: Tire Pressure Monitoring System Tests For Medium and Heavy Trucks and Buses DOT HS 811 314, June 2010 [PDF]
- National Highway Traffic Safety Administration’s Class 8 Tractor/Trailer Safety Outriggers DOT HS 811 289, April 2010
- NHTSA REPORT: "Class 8 Truck Tractor Braking Performance Improvement Study: Low Coefficient of Friction Performance and Stability Plus Parking Brake Evaluations of Four Foundation Brake Configuration". DOT HS 809 753 [PDF,850KB]
- NHTSA REPORT: "Class 8 Truck Tractor Braking Performance Improvement Study, Report 1, Straight Line Stopping Performance on a High Coefficient of Friction Surface". DOT HS 809 700 [PDF, 2.6MB]
Research to Upgrade FMVSS 105 and 121 for Medium and Heavy Duty Vehicles
Current Stopping Distance Requirements for Medium and Heavy Duty Vehicles
|Vehicle Type||Stopping Distance from 60 mph, Empty||Stopping Distance from 60 mph, Loaded|
|Buses (including School Buses)||280 ft||280 ft|
|Single Unit Trucks (except Buses)
|Truck-Tractors with Unbraked Control Trailer||n/a||355 ft|
|Semi-Trailers, Trailers, and Converter Dollies||Dynamometer Requirement||Dynamometer Requirement|
The original, 1970, proposal for FMVSS 121 would have required Buses, Single Unit Trucks, and empty Truck-Tractors to meet a 60 mph stopping distance requirement of 216 feet. (This is identical to the FMVSS 135 light vehicle requirement except for metric system round-off, i.e., the Europeans wanted to have a required stopping distance from 100 kph of 70 meters, not 70.4 meters.) Due to comments and objections from the trucking industry as to their inability, at that time, to meet the 216 feet requirement for all types of medium and heavy duty vehicles, the stopping distance requirements were relaxed to those in force today. However, we believe that due to recent technological advances in medium and heavy duty vehicle brakes, specifically in the area of disk brakes and electronic brake systems (EBS), required stopping distances for these vehicles can be made substantially shorter.
PROGRAM OBJECTIVES: The goal of this program is to perform all of the research necessary to allow Safety Performance Standards to upgrade FMVSS 105 and 121. The upgraded versions of FMVSS 105 and 121 would include:
- Substantially shorter required stopping distances for buses, single unit trucks, and empty truck-tractors on a high coefficient of friction pavement from 60 mph. Revised requirements would be developed both for vehicles with properly functioning brakes and for vehicles with failed systems/ emergency brakes.
- Either increased brake retardation force (this force is measured on a brake dynamometer) or stopping distance requirements for air-braked semi-trailers, trailers, and converter dollies towed by truck tractors. Again, requirements would be developed both for units with properly functioning brakes and for units with failed systems/emergency brakes.
To accomplish the above, this program will focus on medium and heavy duty brake system performance improvements that can be accomplished with upgraded foundation brake systems using various axle configurations for disc brakes, and/or higher output s-cam brakes.