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Have We Seen the Last of Air Brakes For Big Rig Trucks?

It may seem like a hyperbolic question, but there is truth to it. As autonomous technology and electric truck adoption evolve, your good old-fashioned brakes will have to evolve as well. Why? Because autonomous vehicle control systems and battery-electric truck will place new demands on commercial air braking systems. Expect to see brake innovation on the fast-track.

Of course, it is important to note that commercial motor vehicle air brakes have been evolving and changing for the past two decades. It was in 2005 that federal stopping standards forced OEMs to rethink their braking strategy.

From 2005 on, we have seen the addition of significant new safety features, from roll and yaw stability to advanced driver assistance systems. Still, the two trends that are set to change the game again for OEMs are autonomy and electric trucks.

How Will Air Brakes Evolve?

Heavy-duty big rigs have been using air brakes as their primary method of applying stopping force for over 100 years. But it wasn’t until the early 20th century that scaled down versions of air brakes used on trains were applied to commercial trucks.

The reason air brakes became commonly used for big rigs can be traced to the problems associated with using hydraulic brakes in big rigs. Hydraulic braking systems depend on hydraulic fluid contained in a closed system. If there is a problem with the system or it is any way compromised, the brakes may not function at all in stopping the vehicle. Without the fluid, hydraulic systems simply cannot apply the force required.

It is because of those limitations with hydraulic systems that air brakes became the go-to for big truck OEMs. Air brakes are powerful enough to initiate and maintain braking on a large truck and do not need a closed system or hydraulic pressure to apply force. This means they have a built-in redundancy that hydraulic systems do not have.

The Advantages of Air Brake Systems

If a crack in the line develops on an air brake system, if it is not catastrophic, a leak in the air line simply adds more air. Since there is no vacuum loss to contend with, the rig can still achieve stopping power.

The fact is modern air brake systems have lots of advantages for trucking companies and truck OEMs. The technology has been around for a long time and is mature and reliable. Furthermore, technicians already know how to work with air brakes, so there is not a huge learning curve to maintaining them.

Two-circuit braking systems are very robust when it comes to single-point failures. If there is a failure somewhere on the line, the entire system won’t crash. This is a vital function for complex systems needed to support different vehicle combinations. Why? Because there are two primary uses for pneumatics in commercial vehicles: braking and suspension. Provided these systems continue delivering and provide a robust braking solution, they will remain the foundation for any future braking technologies.

Complementary Technologies Evolve

OEMs and trucking companies are now preparing for a highly automated future. And the policies they develop are built around Level 3 autonomous control systems and higher. These policies will become much more commonplace as OEMs build in “mission control systems” into vehicle architecture. The important thing to note is that this approach will differ greatly from current brake control systems.

Electric vehicle adoption will also introduce the ability to simultaneously apply conventional friction for baking and motor-based electric braking. Brake manufacturers are putting a lot of resources into electronically controlled braking systems (ECBS). ECBS are essentially brake-by-wire systems. And while ECBS is relatively new for U.S. trucks, it has been used in Europe for a while now.

Benefits of brake-by-wire systems include enhanced stability controls and a more supportive architecture for regenerative braking systems. Regenerative brakes feed kinetic energy captured whenever the trucker hits the brakes back into the vehicle’s batteries. And even better, ECBS systems are proven and outperform pneumatic systems.

The Many Benefits of Brake-by-Wire

In addition to supporting regenerative braking, ECBS reduces braking delays. Ask any truck driver and they will confirm the widely known 10-millisecond lag between depressing the brake pedal and the onset of force to the wheels. ECBS reduces that delay with the help of electronic brake signals. Additionally, the pressure applied by the brakes is more even than pressure applied by air brakes.

Some ECBS OEMs are reporting stopping distances reduced by as much as 25% when compared to air brake systems. A lower sound threshold is another benefit. Electronic brakes will be much quieter than the hissing and popping everyone hears using air brakes. And for fleets running in urban settings, at night, or in early mornings, lower decibels are better.

Electronic braking systems also raise the efficiency of a truck’s air compressor. This, in turn, allows truck OEMs to reduce weight on their vehicles and ease maintenance demands. Why? Because electronic braking systems have half as many parts as drum or air brake systems. Pneumatic systems will still be needed for other components, such as suspension, but the brakes will be entirely electronically controlled.

Electric Vehicles Bring Electric Brakes

As the industry is pushed to adopt more electric vehicles, electric brakes will become part of the package. Electronic powertrains are a disruptive technology that will push OEMs to use electronic brakes, simply because the two complement each other. Regenerative braking on commercial motor vehicles is just one more example of this shift.

The most important thing is that we are seeing a shift away from foundational brakes for electric vehicles. They simply do not support electronic systems the way ECBS brakes do. It is likely that over time the trucking industry will see a natural optimization of brake systems. And it could be they take baby steps towards it. We are already seeing electronically actuated pneumatic brake systems. With those already in use it won’t be long before we only use electronic brake systems.

Regenerative braking systems also do not wear out as fast as conventional brakes. And they have higher interoperability with complex sensor-based systems on today’s trucks. Expect your technicians to receive alerts when there is a problem with the brakes. And with those alerts will be pinpoint information on the nature of the problem. Troubleshooting and diagnosis on regenerative brakes will be far less of a headache for technicians than with conventional brakes.

Electronic Brakes Go Mainstream

As we mentioned before, brake-by-wire systems have been used in Europe for over 20 years. This makes EBS a logical next step for North American truck OEMs. Even more, innovation is taking hold. North American regenerative brake OEMs are now working on electronic brake and steering integration systems to create multiple redundancy on trucks.

Redundant braking and steering systems allow a vehicle to continue to operate safely should a single system fail. This allows the truck driver to safely reach a rest area or back to the yard.  Ensuring systems never fail creates a safer driving environment for truck drivers.

Yet, as with any time industry adopts a new technology, there may be obstacles to regenerative braking adoption. OEMs will need to develop a redundant air brake control line, as well as redundant CAN brake control lines.

Of course, the challenges to bringing electronic braking systems to North America are many. And to many fleet managers and OEMs, they may seem quite daunting. Yet, there is little doubt that moving to electronic brakes is a logical step to enhance freight efficiency, safety, and modernization as we move into 2022. Some would argue it is a necessary step.

And with the federal government and states pushing for trucking companies to adopt electric and semi-autonomous rigs, the questions surrounding electronic brake systems become not a matter of if, but a matter of when.

In the end, if truck makers want to integrate better brake systems into things like autonomous and hybrid rigs, they will need to add new layers of electronic control systems. Braking performance will need to be improved yet again.

Of course, current air brake systems will provide the foundation by which new systems will be designed. Current braking systems will serve as building blocks for new braking technology in development today. Dual-circuit air brake systems will likely be the mainstay, however, for future brake architecture.

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