California Underride Truck Accidents: Rear And Side Underride Crashes

An underride truck accident can happen when a smaller vehicle travels underneath part of a large truck or trailer during a collision. Because of the height difference between the vehicles, the passenger compartment may come into direct contact with the larger commercial vehicle, creating a risk of severe injuries.

DAG Law Firm, APC represents people injured in serious truck accidents throughout California. Rear and side underride crashes can involve different vehicle movements, safety equipment, and records, so understanding how the collision occurred can be important. You do not pay attorney fees unless we win your case. Call (323) 930-2020 or contact DAG Law Firm today for a free consultation.

What Is An Underride Truck Accident?

An underride crash occurs when part of a smaller passenger vehicle travels beneath the body of a larger truck or trailer.

These collisions can be especially dangerous because the front structure of the smaller vehicle may not absorb the impact in the same way it would during an ordinary car-to-car crash. The larger vehicle can instead make contact closer to the passenger compartment.

Underride crashes are not all the same. Some involve the rear of a trailer, while others involve the side of a truck or trailer.

The type of underride can affect the physical damage, safety equipment, electronic information, and other records that may become important during an investigation.

Rear Underride Truck Accidents

A rear underride collision can happen when the front of a smaller vehicle strikes the back of a larger truck or trailer and travels underneath it.

These crashes may occur in moving traffic, congestion, nighttime conditions, or other situations in which a passenger vehicle approaches the rear of a commercial vehicle.

Questions may involve the speed and movement of both vehicles, braking, visibility, lighting, traffic conditions, and the position of the trailer before impact.

A rear underride does not automatically establish why the collision happened or who was responsible. The entire sequence should be evaluated.

Federal Rear Impact Guards And Underride Protection

Federal safety standards require rear impact protection on many trailers and semitrailers. Rear guards are designed to reduce how far a passenger vehicle can travel underneath a trailer during certain rear collisions.

NHTSA strengthened its rear underride protection standards in 2022. The updated standards increased the performance requirements for guards used on covered trailers and semitrailers.

In 2026, FMCSA removed a separate requirement involving permanent certification labels or markings on rear impact guards. The agency explained that this change did not alter the underlying federal rear-impact protection standards.

Whether a particular trailer required a guard and whether the equipment complied with applicable requirements depends on the trailer and circumstances. A rear impact guard also should not be assumed to prevent every underride collision.

Side Underride Crashes Present Different Issues

A side underride collision occurs when a smaller vehicle travels beneath the side area of a truck or trailer.

These crashes can raise different questions from rear underride collisions because the vehicle movements and impact geometry are different. A side crash may involve an intersection, turning truck, lane change, trailer crossing another vehicle’s path, or other traffic movement.

NHTSA’s June 2024 report to Congress continued evaluating side underride protection for trailers and semitrailers, including effectiveness, feasibility, costs, and potential regulatory approaches.

Investigators may need to examine the truck’s movement, the smaller vehicle’s path, trailer dimensions, visibility, lighting, impact location, and physical damage to understand how the collision happened.

How Underride Truck Accidents Can Happen

There is no single cause of an underride collision.

A crash may involve driver actions, speed, braking, visibility, traffic conditions, trailer movement, lighting, equipment condition, or several factors occurring together.

A rear collision may raise questions about how quickly a passenger vehicle approached a truck, whether either vehicle was braking, and whether the trailer was visible. A side underride may involve different questions about turning, lane position, or a truck crossing another vehicle’s path.

The presence or absence of one piece of equipment should not automatically be treated as explaining the entire crash.

Photos, video, roadway information, witness statements, electronic truck data, and vehicle damage may help provide a more complete picture.

Visibility, Lighting And Truck Maintenance May Matter

Visibility can become important in some underride collisions, especially when a crash happens at night or in poor weather.

Investigators may examine trailer lights, reflective material, roadway lighting, weather, sight distance, and the position of the vehicles. A missing or damaged light does not automatically establish that it caused the collision.

Truck and trailer maintenance may also become important when equipment condition is questioned. Inspection records, maintenance histories, repair invoices, driver reports, and photographs may provide information about the condition of the vehicle before the crash.

Rear guard condition may be particularly important after a rear underride collision. Investigators may need to determine whether damage occurred before the crash or resulted from the impact itself.

Learn more about commercial vehicle maintenance through DAG Law Firm’s guide to California trucking company negligence claims.

Photos And Electronic Truck Data Can Help Explain The Crash

Underride collisions involve vehicle height and impact position, which can make photographs especially useful.

Images may show trailer height, the point of impact, damage to the passenger vehicle, the condition of a rear guard, trailer lighting, reflective material, debris, and final vehicle positions.

Commercial vehicles may also contain electronic systems that provide information about speed, braking, engine activity, driver hours, or other parts of the trip. Different systems record different information.

Electronic data should generally be compared with photos, video, witness statements, roadway marks, collision reports, and physical vehicle damage rather than treated as the only answer.

DAG Law Firm’s guide to California truck accident black box evidence explains how ECM, EDR, ELD, and other truck systems can differ.

Underride Crashes Can Cause Serious Injuries

Underride collisions can cause severe injuries because part of the smaller vehicle may travel beneath a truck or trailer and expose the passenger compartment to direct contact.

Depending on the crash, injuries may include traumatic brain injuries, spinal injuries, neck trauma, fractures, facial injuries, internal injuries, crush injuries, or other serious conditions.

The medical outcome depends on the actual collision. Vehicle speed, impact position, restraints, passenger location, and other factors can affect the severity of the injuries.

Medical professionals are best positioned to diagnose injuries and determine the treatment or future care a person may need.

Readers can learn more about common injuries after a California truck accident.

Who May Be Responsible After An Underride Accident?

Determining responsibility after an underride collision requires understanding how the crash occurred rather than relying only on the type of collision.

Depending on the facts, questions may involve the truck driver, motor carrier, trailer owner, maintenance provider, another driver, or another business connected to the commercial vehicle.

One crash may primarily involve the movements of the drivers. Another may raise questions about trailer equipment, maintenance, visibility, or several issues at the same time.

A company connected to the truck or trailer is not automatically responsible simply because it owned, operated, or serviced part of the equipment.

Learn more about who may be responsible after a California truck accident and California truck accident insurance claims.

Resources And How DAG Law Firm Can Help

Rear and side underride collisions can involve different safety equipment, vehicle movements, and investigation issues. A serious case may require reviewing the truck and trailer, photographs, video, electronic data, rear impact guard condition, lighting, maintenance records, driver information, insurance, and other available records.

DAG Law Firm provides additional resources about California truck accident laws, what to do after a truck accident, who may be responsible after a truck accident, and truck accident black box evidence.

Additional information is available about jackknife truck accidents, trucking company negligence claims, truck accident insurance claims, and common truck accident injuries.

A serious underride accident may require examining several sources together. No single photograph, electronic record, rear guard issue, or company document automatically determines why a crash occurred or who may be responsible.

You do not pay attorney fees unless we win your case. There are no upfront attorney fees for qualifying truck accident matters handled on a contingency-fee basis. Call (323) 930-2020 or contact DAG Law Firm today for a free consultation.