What is an anti-lock braking system (ABS)?

Even the most skilled drivers have faced situations where they needed to slam on the brakes to avoid an accident. In moments like these, a vehicle's wheels can lock up, causing it to lose traction, skid or even spin out of control, making it difficult for the driver to steer safely.

An anti-lock braking system, also called anti-skid braking systems, anti-lock brakes, ABS or even the misnomer ABS brakes addresses this challenge. The system automatically "pulses" or modulates the brakes faster than a human could, allowing the driver to focus on steering.

This system plays a critical role in helping drivers avoid crashes or reduce their damage potential, reducing nonfatal crashes by approximately 6% in cars and 8% in light trucks.¹  Additionally, anti-lock braking systems have been shown to reduce stopping distance. Vehicles equipped with ABS stop 10% to 15% faster than those without it in normal conditions, especially in emergency situations.²

This article will explore how anti-lock brakes work, its different types and how it can improve fleet safety.

How does an anti-lock braking system work?

Anti-lock brakes rely on a system of sensors, pumps, valves and controllers that monitor and adjust brake pressure to prevent wheel lock-up:

• Speed sensors: Located on each wheel, these sensors monitor the speed at which the wheels rotate.
• Valves: Positioned in the brake lines, they regulate brake pressure by opening, closing or releasing as needed.
• Pump: This restores pressure to the brake system when needed, using hydraulic fluid to keep brakes working effectively.
• Controller: This is the system’s “brain.” It constantly monitors wheel speed and if one wheel suddenly slows faster than the others, it signals the valves to pulse to keep the wheels from locking up.

Working together, the anti-lock braking system creates the quick pumping effect that prevents lock-up and allows steering during emergency braking. 

How to use anti-lock brakes

ABS typically engages during sudden or hard braking, such as when traffic stops abruptly or an unexpected hazard appears in the roadway. When the anti-lock braking system activates, the brake pedal may pulse and the brake system may emit a rapid buzzing sound. This indicates that the anti-lock braking system is preventing wheel lock-up and helping the vehicle maintain traction.

During ABS activation, you should apply firm, consistent pressure to the brake pedal and continue steering as needed. If the pedal begins to pulse, resist the instinct to let up or pull your foot off the pedal. Keep steady pressure on the brake and allow the system to manage braking force while you concentrate on maintaining steering control.

You also don’t want to avoid pumping the brakes manually, as the anti-lock braking system already modulates brake force automatically. Once traction is restored, pedal feedback will return to normal. 

While anti-lock brakes may not always shorten stopping distance, it enables greater directional control during emergency braking, bringing a critical advantage for fleet vehicles operating in unpredictable conditions.

Looking for help to enable a safer tomorrow? Learn the steps that set the stage for long-term, sustainable safety results.

Types of anti-lock braking systems

Not all anti-lock braking systems are the same. There are different types of anti-lock brake configurations exist depending on vehicle design and intended use:

• Four-channel, four-sensor ABS: The most advanced system, commonly found in cars, SUVs, minivans and light trucks. Each wheel has its own speed sensor and brake control, providing the highest level of steering control and stability. 
• Three-channel, three-sensor ABS: Typically used on some pickup trucks. Each front wheel has an individual sensor and brake control, while the rear wheels share a single channel. This design improves stability under heavy braking while keeping system costs lower.
• One-channel, one-sensor ABS: Most often found on older trucks, trailers or motorcycles. A single sensor and valve regulate both rear wheels. While it helps prevent rear-wheel lockup, steering control and stability are more limited compared to multi-channel systems.

Can I drive with the ABS light on?

The ABS warning light signals that the anti-lock braking system is not functioning properly. A common question people often have is: Can I drive with the ABS light on? The answer is technically yes. While your standard hydraulic brakes still operate, the additional stability the anti-lock brakes provide during hard braking may be unavailable, increasing the risk of skidding on slick or uneven surfaces. You should therefore exercise extreme caution and get the vehicle inspected immediately to avoid skidding risks.

Common causes include contaminated wheel-speed sensors, low brake fluid, wiring faults, an ABS module malfunction, blown fuses or broken wires. When the light turns on, drivers should report it immediately so the vehicle can be inspected. A persistent ABS warning light can also lead to violations during roadside inspections, making prompt repair essential for both safety and compliance.

Anti-lock braking system regulations for commercial vehicles

An anti-lock braking system is a federally required safety system on most commercial vehicles to help prevent loss-of-control crashes. These regulations apply to both new vehicle manufacturing and ongoing fleet operation. Commercial vehicle ABS rules² require:

• Truck and busses to be equipped with anti-lock braking systems to support braking stability and steering control
• Many trailers, semi-trailers and single-unit trucks to include ABS and functional warning lamps that alert drivers to faults

Anti-lock braking system-related violations can increase downtime, lead to costly repairs and jeopardize fleet compliance. Keeping ABS lamps functional and addressing diagnostic alerts quickly is essential for avoiding enforcement penalties and supporting safer braking performance.

How anti-lock brake systems can help with fleet safety

For fleet managers, anti-lock brakes are an essential feature that can help prevent accidents and reduce maintenance costs by minimizing the risks associated with emergency braking. There are several ways an anti-lock braking system contributes to fleet safety and efficiency:

• Accident reduction: ABS reduces the chance of skidding and allows the driver to maintain control during emergency stops, allowing drivers to safely maneuver away from danger. It can also reduce stopping times under the right conditions.
• Fleet reliability: With fewer skidding incidents and less stress on the braking system, ABS contributes to better overall vehicle health, helping to reduce maintenance needs and associated costs.
• Maintenance reduction: Anti-lock braking systems help reduce tire flat-spotting, brake wear and skidding-related damage, supporting over vehicle health and lower maintenance needs.

How fleet management technology can support anti-lock braking systems

Fleet management technology plays a key role in keeping ABS-equipped vehicles operating safely and reliably. From maintenance tracking to driver coaching, the right tools help fleets monitor brake performance, address issues proactively and reinforce safer driving behaviors.

• Maintenance tracking and alerts: Digital maintenance tools help fleets stay ahead of anti-lock braking system-related issues by tracking service intervals, diagnostic alerts and brake system health. Ensuring ABS warning lamps function properly is essential, as a malfunctioning lamp may indicate a system failure or other brake-related concern.
• Compliance and inspections: Brakes are one of the most frequently cited violations during roadside inspections, and brake defects are a leading cause of out-of-service orders.³ Tools like electronic DVIRs support compliance by standardizing inspection workflows and helping fleets monitor tire pressure, brake linings and brake fluid levels to prevent ABS failures.
• Driver coaching and behavior monitoring: While anti-lock brakes help maintain control in emergency braking, they cannot prevent all crashes. Telematics data and dashcam video allow managers to identify risky habits — such as tailgating, speeding or hard braking — and deliver targeted coaching to reinforce proper following distances and defensive driving in poor conditions.

By reducing skidding, preventing wheel lock-up, and allowing drivers to maintain control in emergencies, anti-lock brakes help to improve safety, reduce maintenance costs and enhance fleet efficiency. To further promote fleet safety, consider using fleet management software to track maintenance of anti-lock braking systems, monitor driver behavior and stay on top of preventive maintenance.

For a closer look at how fleet management software can enhance your fleet’s safety and efficiency, consider booking a demo today.

Sources

¹ https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811182

² https://www.ecfr.gov/current/title-49/subtitle-B/chapter-III/subchapter-B/part-393/subpart-C/section-393.55

³ https://cvsa.org/news/2025-bsw-results/