How to Properly Stop with Air Brakes

To stop correctly with air brakes, look far ahead, ease off the throttle early, apply firm, progressive pressure to the service brake pedal while accounting for air-brake lag, use lower gears and engine braking where appropriate, avoid pumping the brakes (especially with ABS), and switch to snub braking on long downgrades; in emergencies, use controlled braking with ABS or stab braking if no ABS, and pull over immediately if a low-air warning activates. This guidance helps you stop smoothly, safely, and without overheating or depleting air pressure.

Why Technique Matters With Air Brakes

Air brake systems on heavy trucks and buses deliver strong, reliable stopping power, but they behave differently from hydraulic systems. There’s a small delay—air-brake lag—between pedal application and brake force at the wheels, typically around four-tenths of a second. At highway speeds, that lag alone can add roughly 30 feet or more to stopping distance. Proper technique compensates for this lag, prevents brake fade on grades, and preserves air pressure so the spring (parking/emergency) brakes never need to intervene while moving.

Understanding the System: Pressure, Lag, and ABS

Normal system pressure typically runs about 90–120 psi, with the governor cutting out near 120–125 psi and cutting in near 100 psi. A low-air warning should trigger around 55–75 psi; if it does, you must stop safely and investigate. Modern fleets are equipped with ABS; with ABS you should apply firm, steady pressure and steer—do not pump the brakes. Without ABS, certain emergency techniques differ, as noted below.

Step-by-Step: Normal Stops

The following sequence shows how to perform a smooth, controlled stop with air brakes during everyday driving.

1. Scan ahead 12–15 seconds, check mirrors, and signal early to avoid last-second braking.
2. Ease off the throttle and align the vehicle in your lane; cover the brake pedal.
3. Begin braking sooner than you would in a car to account for air-brake lag and added mass.
4. Apply progressive pressure: firm, smooth input that increases as needed without abrupt spikes.
5. Downshift early as appropriate for your transmission; engage engine braking/retarder on dry pavement to assist, but turn the retarder off on slippery surfaces.
6. Keep eyes moving: monitor traffic, mirrors, and your air pressure gauges; avoid “riding” the brakes.
7. As speed drops, ease off brake pressure to prevent a harsh stop; bring the vehicle to rest smoothly behind the stop line.
8. Once stopped, hold the service brake; if parking, set the parking (spring) brakes after ensuring adequate tank pressure.

This method balances vehicle dynamics and brake system characteristics, delivering predictable stops while preserving brake components and air supply.

Emergency Braking: ABS vs. Non-ABS

Know your equipment before an emergency. The technique depends on whether your vehicle has ABS.

• With ABS: Apply hard, steady brake pressure and steer around hazards. Do not pump the brakes; ABS modulates pressure for you.
• Without ABS: Use controlled braking—apply as hard as possible without locking wheels, then steer as needed. If wheels lock, release just enough to regain traction.
• Stab braking (non-ABS only): Firmly apply until wheels lock, immediately release to let them roll, then reapply once traction returns. Do not use this with ABS.

In all cases, look where you want to go, maintain lane control, and prioritize stability. After the stop, assess brake temperatures and air pressure before proceeding.

Long Downgrades: Preventing Brake Fade

Continuous braking on long or steep grades can overheat linings and drums/rotors, causing fade and longer stopping distances. Use gearing and a disciplined technique.

• Select a low gear before the grade; let engine braking carry most of the load.
• Use snub braking: when speed rises to your maximum safe speed, apply firm pressure to reduce speed by 5–10 mph, then fully release to let brakes cool; repeat as needed.
• Avoid light, continuous braking that keeps drums hot and encourages fade.
• Monitor brake odor, smoke, or pull—signs of overheating or imbalance—and watch air pressure closely.

Snub braking, combined with proper gearing, keeps brakes cooler, maintains reserve stopping power, and preserves air supply throughout the descent.

Stopping on Slippery or Wet Surfaces

Reduced traction requires gentler inputs to maintain control. Adjust technique to the conditions below.

• Lengthen your following distance and begin braking earlier to offset reduced grip and air-brake lag.
• Disable the engine retarder on ice, snow, or slick rain to prevent drive-axle skids.
• Apply smooth, progressive pedal pressure; avoid sudden steering or downshifts that could unsettle the vehicle.
• With ABS, maintain steady pedal pressure; without ABS, modulate to avoid lockup.

These adjustments help you maintain traction and vehicle stability, preventing wheel lock and jackknifing in low-traction environments.

What to Watch on Your Gauges and Indicators

Proactive monitoring prevents surprises during braking. Keep an eye on the following cues.

• Air pressure: Normal range is typically 90–120 psi; confirm proper governor cut-in/-out behavior.
• Low-air warning: If it activates (often 55–75 psi), stop safely, secure the vehicle, and investigate; do not continue driving.
• Application pressure: Unusually high pedal/application pressure for routine stops can indicate fade, out-of-adjustment brakes, or a system issue.
• ABS warning lamp: If illuminated, ABS faulted; braking reverts to conventional air brakes—adjust technique accordingly.

Early recognition of these signs allows timely corrective action, reducing risk of brake loss or extended stopping distances.

Common Mistakes to Avoid

These frequent errors can degrade stopping performance, overheat brakes, or compromise safety.

• Pumping the brakes with ABS-equipped vehicles (lengthens stops and confuses the system).
• Continuous light braking on grades (promotes heat build-up and fade).
• Riding the brakes in traffic (wastes air and overheats components).
• Relying on spring brakes to stop a moving vehicle (they are for parking/emergency, not controlled stops).
• Leaving the retarder on in slick conditions (can cause drive-axle skids).
• Ignoring low-air warnings or abnormal governor operation.

Avoiding these pitfalls preserves stopping capability and extends component life while preventing emergencies.

Parking and Post-Stop Safety

Once you’ve come to a complete stop, secure the vehicle correctly to prevent rollaway and protect your braking system.

• Hold the service brake, place the transmission in neutral (or appropriate park position), and set the parking (spring) brakes after verifying sufficient air pressure.
• On grades, turn wheels toward the curb (downhill) or away (uphill, if there’s a curb) and use wheel chocks as required by company policy or local rules.
• After heavy braking or a long downgrade, allow a cool-down period and, if safe, perform a walk-around to check for smoke, odor, or hot hubs.

These steps ensure the vehicle remains secured and that any heat-related issues are addressed before resuming travel.

Key Numbers and Practical Benchmarks

These reference points help calibrate expectations and decision-making while stopping.

• Air-brake lag: roughly 0.3–0.5 seconds; at 55 mph, 0.4 seconds adds about 30–35 feet to stopping distance.
• Look ahead: 12–15 seconds in urban settings; up to a quarter mile on highways.
• Following distance (heavy vehicles): about 1 second per 10 feet of vehicle length under 40 mph; add 1 second above 40 mph.
• Normal pressure: approximately 90–120 psi; low-air warning around 55–75 psi; spring brakes begin to apply near 20–45 psi.

Using these figures keeps your planning realistic and your technique matched to the vehicle’s braking characteristics.

Summary

To stop properly with air brakes, anticipate early, apply smooth and progressive pedal pressure, and let gearing and engine braking do their share—especially on grades. With ABS, hold firm pressure and steer; without ABS, use controlled or stab braking only in emergencies. Monitor air pressure and warnings, avoid riding or pumping the brakes, and switch to snub braking on long descents. These practices minimize stopping distances, reduce heat and wear, and maintain full system readiness when you need it most.

What are 7 steps air brakes?

Click here for help finding your state’s manual.

• Step 1: Turn the Key to the “On” Position.
• Step 2: Fan the Service Brake Below 90 PSI.
• Step 3: Identify Air Pressure Levels.
• Step 4: Perform a Safety Start.
• Step 5: Fill the Air Chambers.
• Step 6: Apply and Hold the Service Brake.
• Step 7: Check and Record Air Pressure.

How to properly brake with air brakes?

To use air brakes, press the brake pedal to apply the service brakes, increasing air pressure for more stopping force. To park, pull the diamond-shaped, yellow parking brake knob to release air from the chambers and engage the spring brakes. Before driving, ensure the parking brake knob is pushed in, the system has sufficient air pressure, and the low air warning light isn’t on.
 
How to Apply the Service Brakes (Normal Stopping)

1. Press the brake pedal: Opens in new tabPush the foot brake pedal down to apply air pressure to the brake chambers. 
2. Increase pressure gradually: Opens in new tabMore pressure on the pedal means more air is released, applying more braking force. 
3. Release the pedal: Opens in new tabWhen you’re nearly stopped, let up on the brake pedal to reduce air pressure and release the brakes. 

How to Engage the Parking Brakes

1. Check air pressure: Ensure you have adequate air pressure in the system. 
2. Engage the parking brake: Pull the yellow, diamond-shaped control knob out to release the air from the brake chambers, which allows the power springs to engage and apply the brakes. 
3. Select a gear (if applicable): Place the transmission in a starting gear before disengaging the parking brake, if using a manual transmission. 

Before You Drive

1. Push the parking brake knob in: Opens in new tabTo release the parking brakes, push the yellow knob back in to allow air into the brake chambers. 
2. Start the engine: Opens in new tabThe air compressor will then begin to build air pressure. 
3. Monitor air pressure: Opens in new tabWatch the dashboard air pressure gauges to ensure the system reaches a safe operating pressure. 
4. Check for leaks: Opens in new tabPump the brakes several times to confirm the low air pressure warning light comes on around 60 PSI. 
5. Confirm brakes release: Opens in new tabContinue to fan the pedal until the air pressure is low enough for the parking brake to automatically come on. The vehicle should not move. 

How do you stop a vehicle using air brakes?

You engage the brakes by pushing down the brake pedal (It is also called a foot valve or treadle valve). Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes.

What should you do for a normal stop with air brakes?

For a normal stop with air brakes, you should apply steady and controlled pressure to the brake pedal (also called the foot valve or treadle valve) to gradually slow the vehicle to a smooth, safe stop. Start braking early and gradually increase pressure as needed. Release the pedal to reduce air pressure and disengage the brakes. 
Here’s a step-by-step guide:

1. Start braking early: Begin slowing down well in advance of your stopping point, as air brakes can have a lag and take longer to engage than hydraulic brakes. 
2. Apply the brake pedal: Push the brake pedal down to the necessary level to control the vehicle. 
3. Apply pressure gradually: Increase the pressure on the pedal as needed to achieve a smooth, controlled deceleration. 
4. Control the stop: Continue applying pressure until the vehicle comes to a complete and safe stop. 
5. Release the brake pedal: Once stopped, release the pedal to relieve the air pressure and allow the brakes to disengage. 
6. Shift to a starting gear (if applicable): If you have a manual transmission, don’t push the clutch in until your engine RPMs are close to idle. 
7. Select a starting gear: Once stopped, select the appropriate gear for moving forward. 

Important tips for air brakes:

• Look ahead: Anticipate traffic and events to avoid sudden stops. 
• Practice: Get used to the feel of air brakes by practicing in a safe environment. 
• Understand air pressure: Be aware that air pressure holds the brakes off, and losing air pressure can engage the emergency and parking brakes. 
• Be gentle: Avoid slamming on the brakes, as this can lock the wheels and make it harder to control the vehicle.