What Is an Underride Accident?

An underride accident is a collision that happens when a smaller car hits a large truck and slides underneath the trailer. When a car slides underneath a truck, the top of the vehicle is typically sheared off, decapitating or crushing the passengers inside, making underride accidents some of the deadliest types of crashes, even at relatively low speeds.

There are two main types of truck underride accidents:

• Side underride accidents. These are accidents that happen when a smaller vehicle hits the side of a truck. Side underride accidents usually occur at night or when the sun is at a low angle, or when a trucker is attempting to make a U-turn, cross or turn on a street, or back across traffic and other vehicles do not see the truck crossing their paths. Although truck drivers often assume that on-coming drivers can see them crossing the road, these drivers may not see a truck entering their path until it is too late.
• Rear underride accidents. These accidents happen when a car hits the rear of a large truck and slides under it. Rear underride accidents can happen when a truck is poorly marked, is parked at the side of the road, slows down for an intersection or railroad crossing, slowly enters a road, or exits a highway too slowly. Dim or burned-out taillights can also lead to rear underride accidents because if the vehicle’s driver doesn’t realize a truck is traveling slowly, they might not hit the brakes in time to avoid the collision.

If the impact occurs near one of the truck’s axles, the smaller vehicle might be prevented from going completely under the truck, giving the passengers a better chance of survival.

Causes of underride accidents

There are several common reasons underride accidents occur. These include:

• Rain, fog, or other weather conditions make it difficult for drivers to see trucks and easier for truck drivers to lose control
• Cars that tailgate trucks or follow too closely to avoid a rear-end collision
• Drivers that travel too fast for the road conditions
• Negligent truckers that do not make their presence known to the drivers around them

To avoid underride accidents, truckers should ensure that all truck lights are working correctly, be extremely careful when entering or exiting roads, and signal so that other drivers know they intend to come to a stop.

Underride guards – Jayne Mansfield’s legacy

For the last few decades, large trucks have been required to be equipped with underride guards, also known as rear safety bars or “Mansfield bars,” to prevent underride accidents. These steel bars mounted beneath the rear of semi-trucks and tractor-trailers help prevent smaller vehicles from rolling underneath trucks during a rear-end collision. However, because the DOT does not require guard inspections, not all rear guards are as effective as they could be. Drivers who do not use proper underride guards, fail to keep their trucks properly maintained, don’t use or maintain vehicle lights, and neglect to meet conspicuity standards can be held negligent for an underride accident.

In June 1967, actress Jayne Mansfield and three other adults died instantly when the 1966 Buick Electra they were traveling in slid beneath a slow-moving semi. Mansfield’s three children asleep in the backseat, including “Law & Order: SVU” star Mariska Hargitay (then three years old), miraculously survived the collision. Shortly after the crash, the National Highway Traffic Safety Administration called for the addition of underride prevention guards on large trucks; however, the requirement wasn’t fully implemented until 1998. At that time, the NHTSA estimated that as many as 300 deaths occurred annually due to underride accidents

“Target conspicuity” essential to reduce underride collisions

Greater target conspicuity – how well a vehicle stands out from its background – can reduce the incidence of side underride accidents, particularly at night, when it can be challenging to see a truck. There is a general misconception that the large size of trucks makes them conspicuous, but size is only one of the factors that create contrast between the truck and its background.

Due to the severity of trailer underride collisions, the U.S. Department of Transportation (DOT) mandates conspicuity markings for all trailers. This requirement is met by using retroreflective tape capable of reflecting light back to the source at great distances. The tape must be two inches tall, have a red and white alternating pattern, and placed on the sides and rear of the trailer 15 to 60 inches from the ground.

On the sides, the tape must be evenly spaced and cover a minimum of 50 percent of the length of the trailer. On the rear, the tape is required to cover the full width of the trailer, with four 12-inch white stripes designating the top corners. These standardized markings show the size and shape of the trailer, and the highly reflective surface and red and white color creates contrast against the dark background to allow trailers to be seen by approaching drivers.

Although the retroreflective tape is effective in making trailers visually stand out, a trucker should never assume that this tape will guarantee that the trailer will be seen. If the tape is dirty, in bad condition, or the truck is at a steep angle to traffic, approaching drivers still may not see the trailer, and the is of an underride accident remains. In the absence of any lighting reflecting off the painted surface of the trailer, it will appear black against the black background and an approaching driver will need to rely on the side marker lights to indicate the presence of the trailer. However, even when marker lights are legally positioned on the sides of the trailer, oncoming drivers may not recognize the trailer as an obstruction blocking their path.

Phelan Petty is a Virginia law firm dedicated to protecting the rights of those injured in truck accidents occurring in the greater Richmond area. If you or a loved one has sustained serious harm in a truck underride accident, contact us at to set up your free initial case evaluation today.

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