Editor’s Note: This is the first part of a two-part series on how safety and TCO can improve with next-generation braking systems.
Vehicles in the United States traveled 13% fewer kilometers in 2020 than in 2019, but the number of road fatalities increased by 8% to 42,060 – the highest in 13 years, according to the National Safety Council (NSC).
“The number of road fatalities is alarming,” said Elaine Martin, President and CEO of NSC. “But the death rate is even more worrying. The United States saw a staggering 24% increase in the rate of fatalities per 100 million vehicle-miles on our roads last year. This is the largest year-over-year increase we’ve reported since the board started calculating it almost a century ago. ”
Three million more people are injured in crashes each year, costing US $ 460 billion. Martin acknowledged “it is too early to determine the full cause”, although road systems poorly adapted to modern driver errors were seen as a factor.
The COVID-19 pandemic and the mental and emotional stress it created have likely also had an impact on driver behavior. The National Highway Traffic Safety Administration has found in the early stages of the lockdown pandemic: “Among the drivers who remained on the roads, some engaged in riskier behaviors, including speeding, not wearing seat belts and driving under the influence of the alcohol or other drugs. ”
In a study conducted by five trauma centers between mid-March and mid-July, nearly two in three drivers brought in after a serious or fatal crash tested positive for alcohol, marijuana, opioids or other drugs. After mid-March, positive opioid tests nearly doubled and marijuana use increased by about 50%.
There are a myriad of other reasons the roads have become more dangerous, such as speeding (which fleets did 20% more frequently last April, according to Samsara). But the main thing is that the roads are becoming more and more unpredictable and the fleets must improve their defensive strategy.
At some point, that will likely include the adoption of advanced driver assistance systems (ADAS) such as collision mitigation and automatic emergency braking. According to Rand Corporation’s Road to Zero report, this technology would save 10,000 lives per year if the current range of ADAS were available on every vehicle. Daimler Trucks’ Detroit Assurance 5.0, for example, can detect pedestrians using radar and camera sensors, and it will partially or fully activate emergency braking if the driver does not respond to visual and audible alerts.
But fleets don’t necessarily focus entirely on high-tech solutions to improve their safety. They can start by simply reassessing how the trucks stop. This includes basic brakes, engine braking and, for the new wave of electrified trucks, regenerative braking.
If a fleet is to put its drivers, equipment and cargo in the safest possible position, it must have the best braking systems and the best technology that is financially feasible. Fortunately, there are many advances in modern braking that reduce stopping distance and maintain or improve the total cost of ownership of legacy systems, allowing fleets to break even while dramatically improving stopping power.
And after safety performance, the TCO of a braking system is a very real concern and a limiting factor for fleets. Like tires, brakes wear out the more they are used. Maintenance and brake replacement are the highest costs for many fleets.
This varies widely depending on the duty cycle and location. A garbage truck that stops at every house in a neighborhood puts its brakes through a workout each day, while highway trucks often only need to press the brakes to adjust speed in. because of traffic. A long-haul truck going through the congestion of downtown Chicago or slowing down the Rocky Mountain peaks of Interstate-70 in Colorado will need brake linings replaced much more often than a regional carrier in Texas.
Fleets with higher brake wear will inevitably have shorter replacement intervals and the downtime that goes with it. But regardless of the fleet, reviewing the type of brakes used and how drivers and service technicians are trained to use and work on them will result in better safety scores and manageable maintenance costs.
Pneumatic disc brakes
Over the past decade, due to the enactment by the National Highway Traffic Safety Administration of regulations on shorter stopping distances (FMVSS 121), brake manufacturers have deployed new materials and components to improve the performance of the brake system. Two-axle tractors and 6×4 tractors over 59,600 lbs. The gross vehicle weight rating threshold should stop within 250 feet when traveling at 60 mph and towing a trailer. Previously, he was 355 feet tall. This allowed air disc brakes (ADB) to finally gain a foothold in North America.
In addition to electronic braking systems (EBS), air disc brakes have been common on European trucks for two decades. According to Swedish brake manufacturer Haldex, the acceptance rate for EBS / ADB configurations was 70% in 2000. This number now exceeds 80%.
In North America, the catch rate hovers just below 50%, according to Meritor – up from 15% in 2015. ADB EX + LS recently launched by Meritor are standard on Freightliner Cascadias of model year 2022.
The lightweight EX + LS also meets the U.S. Environmental Protection Agency’s 2025 copper reduction standards, adopted to prevent copper from entering the water supply.
Meritor Engineering Director Joseph Kay also noted that these brakes are compatible with trailers equipped with drum brakes and will not “displace that balance of wear between tractor and trailer.”
ADBs, which include a wheel hub assembly, brake caliper assembly, and disc rotor, have several advantages over S-cam drum brakes. The first is performance. Air disc brakes have demonstrated the ability to stop a 6×4 truck going 100 km / h in 200 feet, while a drum brake would take 225 feet, according to Bendix Commercial Vehicle Systems tests.
Pitt Ohio, a fleet of 1,400 power units, began the transition to ADBs two years ago, although not all units have it yet. Jeff Mercadante, vice president of safety, recalled seeing how Bendix ADB22X air disc brakes worked on a test track, where a truck with ADB traveling at 55 mph stopped 15 feet shorter than ‘one with drum brakes. “Fifteen feet is the length of a car,” said Mercadante. “When you hit 70 km / h you’re talking closer to 50 to 60 feet.”
So far, Pitt Ohio has seen the improvements materialize on the road. “Our rear-end collisions happened because of the air disc brakes and the [Bendix Wingman Fusion’s] anti-collision system at the front, ”explained Mercadante.
The Wingman Fusion system will recognize if the truck is following too close to the vehicle in front, alerting the driver when the vehicle is half a second away from the collision. If the driver does not slow down, the Bendix electronic stability platform will take control of the brakes. It is important to tell operators that the faster the truck travels, the less reaction time there is.
“Overall, the system will mitigate around 70% of the number of rear end accidents and an additional 70% of the severity of those that remain,” said TJ Thomas, director of marketing and customer solutions for Bendix Group. control.
Improvements to this safety metric started in the training room.
“We brought in Bendix trainers to our facilities and educated the technicians on how they worked and how to maintain them and how to inspect them,” said Taki Darakos, vice president of vehicle maintenance and fleet services. from Pitt Ohio. It was before the pandemic, so it was a more hands-on experience. Once drivers started using them, reviews were overwhelmingly positive for the “car feel” of the new brakes and significantly improved stopping distance.
Pitt Ohio will continue to transition its heavy vehicle fleet with ADBs as it renews with new trucks. While replacing the drums on trailers is a consideration, it’s not as vital as the trailer brake wear items in Pitt Ohio require less frequent replacements.
“We’ve got a couple thousand trailers and an air disc brake upgrade that takes time and money, and then you sacrifice something somewhere else,” Darakos said.
Blasé by fading
Another advantage is how ADBs maintain consistent performance despite extended periods of use, while drum brakes are sensitive to the heat built up by friction.
“A drum brake experiences a phenomenon called fading,” said Keith McComsey, director of the air disc brake product group at Bendix Commercial Vehicle Systems. Brake discoloration can occur as the drum heats up to a point where it begins to expand away from the friction material, causing stopping performance to deteriorate. A longer push rod stroke will be required for the brake to contact the friction surface of the drum.
“With air disc brakes, you basically have two pads that press against the rotor, and as that rotor heats up, it thermally expands towards the friction, so you don’t have the same phenomenon,” McComsey explained. .
The second part will explore the ways in which air disc brakes can generate new benefits in terms of total cost of ownership.