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How do you control jackknife?

What is jackknifing?

Jackknifing is when the cab and trailer of an articulated truck fold over each other, resembling a folding pocket knife. This can occur when the driver locks up the trailer brakes only, causing them to skid while the still-rolling cab swings around. Jackknifing is dangerous as it can result in loss of control and a rollover crash. It’s an inherent risk with tractor-trailers and particularly likely when traveling at high speeds, on wet/icy roads, or with an improper load balance.

What causes a jackknife?

There are a few key factors that can cause a tractor-trailer to jackknife:

Trailer brakes lock up

If the trailer brakes are applied too aggressively, they may lock up while the tractor continues rolling forward. This pivots the trailer around the fifth wheel.

Sudden steering input

A quick turn of the steering wheel can swing the rear of the tractor out, initiating a jackknife.

Slippery road conditions

Wet, icy or snow-covered roads reduce available traction, making it easier for the trailer to swing out.

High speeds

The higher the speed, the more force applied when braking or turning, increasing the chance of a jackknife.

Improper load distribution

Too much weight toward the back of the trailer can cause swaying, leading to instability.

How can truck drivers prevent a jackknife?

There are defensive driving techniques all truckers should practice to reduce the risk of jackknifing:

Stabilize trailer before braking

When needing to slow down, take your foot off the accelerator and allow the truck to start naturally slowing before braking. This gives the load a chance to settle forward.

Brake slowly and gradually

Slamming on the brakes increases the chance of trailer lockup. Brake early and progressively to smoothly decelerate.

Avoid sudden turns

Make slow, wide turns whenever possible. Sudden sharp turns while traveling fast heighten jackknife risk.

Control speed in hazardous conditions

Slow down well below the posted limit when roads are wet, snowy or icy to avoid skidding.

Distribute weight properly

Consult federal weight limits and balance the load so no more than 60% of total weight is on/behind the trailer axle(s).

How can fleets and trucking companies reduce jackknifes?

In addition to training drivers on safe operating techniques, there are some best practices transportation companies can implement:

Fleet Safety Measure How It Prevents Jackknifes
Regular trailer maintenance Ensures brakes are in good working order and reduces failure risk
Good tire condition/traction Helps grip the road and avoid skidding in bad weather
Stability control systems Automatically controls brakes to stop trailer sway
Side underride guards Prevents a car from sliding under the trailer in a crash
Speed governors Caps truck speed to a safe maximum

Regular Trailer Maintenance

Consistently checking and servicing trailer components like brakes, tires, and axles lowers the chance of failure that could initiate a jackknife. Follow the manufacturer’s maintenance schedule and perform pre-trip inspections.

Good Tire Condition/Traction

Make sure tires are properly inflated and have ample tread depth for wet weather traction. Replace worn tires and consider using all-weather or snow tires in icy climates.

Stability Control Systems

Electronic Stability Control applies brakes selectively to individual wheels when it detects trailer sway. This automatically counteracts the swing and stabilizes the rig.

Side Underride Guards

These prevent smaller vehicles from sliding under the trailer in a collision. This helps maintain stability in a crash scenario.

Speed Governors

These limit top speed to improve control. Set at 60-65 mph maximum to reduce high speed jackknife risk. Governors also improve fuel efficiency.

What to do if you’re in a jackknife

Jackknifing happens quickly, usually leaving few options other than trying to recover or brace for impact. Here are tips if you find your rig starting to jackknife:

Avoid the brakes

Trailer brake lockup is a major cause of jackknifing. Release the brakes if already applied. This will allow wheels to roll/gain traction.

Countersteer the skid

Turn the steering wheel in the direction of the jackknife. This helps straighten out the rig. Don’t overcorrect or you risk swinging the other way.

Stay off the accelerator

More power will only push the jackknife further out of control.

Hold the wheel firmly

Keep a solid grip on the steering wheel. The trailer swinging will jerk it strongly in the opposite direction.

Stay focused on recovering

Concentrate fully on bringing the rig back in line. Don’t panic or freeze up.

Brace for a crash

If all efforts fail, prepare for an impact. Wear your seatbelt, grasp the wheel tightly, and turn away from the point of collision.

How to deal with jackknife accidents

In the aftermath of a jackknife accident, it’s important to follow safety protocol:

Check for injuries

Make sure you and any passengers are unharmed before assessing the vehicles. Call emergency services immediately if medical help is needed.

Secure the scene

Turn on hazard lights, set out flares/triangles, and move off the road if possible. This prevents secondary collisions with the disabled vehicles.

Document evidence from vehicles/scene

Take photos of skid marks, vehicle damage, weather conditions, etc. that may be relevant in determining fault.

Contact company/authorities

Report the accident to your fleet manager per company policy. Also call the police to file an official report.

Exchange info with other parties

If another vehicle is involved, swap insurance and contact details in case claims arise later. Get witness contact info also.

Undergo drug/alcohol testing

As mandated after accidents, submit to required substance screening. Refusal could be grounds for firing.

Review prevention practices

Carefully analyzing how the jackknife occurred can reveal weaknesses in training or procedures to improve. Additional driver education may help too.


Jackknifing is a complex phenomenon but one preventable through quality driver training, safe operating practices, and proactive fleet management. Defensive techniques like gradual braking and speed control in hazardous conditions can help avoid trailer swing-out. Professional truckers must also know how to correctly recover control and minimize damage if a jackknife does start to occur. While an ever-present risk, jackknifes can be effectively minimized through rigorous safety standards. This keeps truckers, shippers, and the traveling public better protected on the roads.