Semi trucks can have air brakes with or without ABS (Anti-lock Braking System). ABS improves safety by preventing wheel lock-up, keeping the truck stable and controllable during hard braking — especially on slippery roads.

Without ABS, wheels can lock, increasing the risk of skidding, jackknifing, and longer stopping distances.

With ABS vs Without ABS animation video.

With ABS vs Without ABS :

Braking Control:

With ABS, the system prevents wheel lock-up during sudden or hard braking. This keeps the tires rotating, allowing the driver to maintain steering control.

Without ABS, the wheels can lock up, leading to skidding and loss of control.

Stopping Distance:

ABS usually shortens stopping distance on wet, icy, or slippery surfaces because the tires maintain traction.

Without ABS, locked wheels slide across the road surface, which can actually increase stopping distance.

Vehicle Stability:

ABS improves stability by modulating brake pressure individually at each wheel. This helps prevent jackknifing or trailer swing.

Non-ABS systems lack this control, making the truck more likely to skid or lose balance during emergency braking.

Driver Control:

ABS lets the driver steer while braking hard — an essential feature when avoiding obstacles.

Without ABS, locked wheels prevent the driver from changing direction effectively, which can result in crashes.

Tire Wear:

Because ABS avoids wheel lock-up, it reduces flat-spotting and uneven tire wear.

Without ABS, frequent wheel lock-ups can damage tires and lead to premature replacement.

Maintenance:

ABS systems are more complex, requiring sensors, wiring, and an electronic controller that need periodic checks.

Traditional air brakes without ABS are simpler, making them easier and cheaper to maintain.

Cost:

ABS-equipped trucks are more expensive to build and repair due to the added electronic components.

Trucks without ABS have lower upfront and maintenance costs, though they compromise on safety.

Regulations:

In many countries, including the U.S., ABS is mandatory on most air-braked vehicles manufactured after the late 1990s.

Non-ABS trucks are usually older models that predate these regulations.

Overall Safety:

ABS greatly improves safety, especially in emergency situations and poor weather.

Non-ABS systems increase the risk of skidding, jackknifing, and losing control — which is why ABS has become standard on modern trucks.

Summary:

ABS-equipped air brakes provide better control, stability, and safety, especially on wet, icy, or uneven roads. The trade-off is slightly higher cost and maintenance complexity, but the safety benefits far outweigh the downsides — which is why ABS is now standard on modern semi trucks.