Jackknife accidents typically start when a tractor-trailer’s wheels lose grip during hard braking, usually because of slick pavement, speed that is too high for conditions, uneven or faulty brakes, or a lightly loaded trailer, and they are prevented mainly by slowing down early, keeping brakes in working order, and leaving enough room to stop gently.
Understanding the factors that cause these crashes can help injured victims determine their legal options and pursue compensation for your bills, including medical expenses and other accident-related losses.
In this post, we will cover what causes jackknifes, how common they really are, and what drivers and carriers can do to prevent them.
Understanding Jackknife Truck Accidents
State commercial driver manuals describe two kinds. In a tractor jackknife, the drive wheels lock and the trailer pushes the tractor around, while in a trailer jackknife, the trailer wheels lock and the trailer swings out, which the manuals say is more likely when the trailer is empty or lightly loaded.
Common Causes of Truck Jackknife Accidents
- A sudden stop forced by another driver: The FMCSA says trucks can need up to two football fields to stop at highway speed, and that cutting in front of one shrinks its safe stopping room.
- Brake problems: FMCSA’s Large Truck Crash Causation Study coded brake problems for almost 30 percent of the trucks in its sample, compared with 5 percent of passenger vehicles, although that shows a link rather than proof of cause.
- Hard braking on slick pavement: Wet, icy, or snowy roads reduce traction, and once wheels lock, the trailer or tractor can swing around.
- Speed that is too high for conditions: More speed means more momentum, and that is why the rules below tell drivers to slow down when traction drops.
- An empty or lightly loaded trailer: The driver manuals say large combinations can take longer to stop empty than fully loaded.
How Common Are Jackknife Accidents?
Less common than most people assume. FMCSA figures built on NHTSA data show 169 of 4,842 large trucks in fatal crashes in 2020 jackknifed, about 3.5 percent, and in 142 of those the jackknife followed some other event, with only 27 being the first event in the crash.
Preventing Jackknife Truck Accidents
Federal regulations establish several safety measures to help reduce the risk of jackknife truck accidents. Under 49 CFR 392.14, truck drivers must exercise extreme caution in hazardous conditions such as rain, snow, ice, and fog. They must reduce speed and stop driving when conditions become too dangerous to continue safely.
49 CFR 396.3 requires motor carriers to systematically inspect, repair, and maintain their vehicles. Proper maintenance helps identify brake problems, tire defects, and other mechanical issues that could contribute to a jackknife accident.
Additionally, 49 CFR 571.136 establishes electronic stability control requirements for applicable new truck tractors. This technology helps drivers maintain control and reduces the risk of certain loss-of-control crashes. Together, cautious driving, regular vehicle maintenance, and appropriate safety technology can help prevent jackknife accidents.
What Else Helps?
- Working antilock brakes, which NHTSA has required on new tractors since 1997 and air-braked trailers since 1998, and which its study linked to a large drop in jackknifes.
- Braking with the foot brake alone, since the driver manual notes this carries much less risk of a skid or jackknife.
- Other drivers staying out of blind spots and never cutting in close, which is also FMCSA advice.
Quick Summary
- Jackknifes typically begin with hard braking when wheels lose grip.
- Slick roads, excess speed, brake problems, and light trailers all raise the risk.
- In 2,020 fatal crash data, most jackknives followed another event.
- 49 CFR 392.14 requires slower speeds when conditions affect traction.
- Antilock brakes and stability control help only when they work.
- Leaving trucks’ rooms to stop protects everyone around them.
