There is more large truck traffic here in Illinois and Indiana than in other parts of the country because we are an international commercial hub recognized as the “Crossroads of America.” The greater number of 18-wheelers, big rigs, tractor trailers, and semi-trucks on our roadways obviously increases our risk of being involved in a catastrophic or fatal truck crash. See, Semi Trucks and Big Rigs: High Indiana and Illinois Commercial Truck Traffic Creates Dangerous Conditions.
For safety agencies and advocates for truck crash victims and their loved ones, perhaps the most horrific danger on our truck routes today is the collision between a passenger vehicle and a rig where the smaller car, van, SUV, or pickup gets caught underneath the big truck. These are known as “underride accidents” and they can happen in several different ways.
What is An Underride Accident?
A definition of an underride accident is found in Section 23011(c) of federal legislation known as the “Bipartisan Infrastructure Law,” “… in which a trailer or semitrailer intrudes into the passenger compartment of a passenger motor vehicle.”
Imagine a tractor-trailer truck rumbling alongside your car on I-57, I-55, I-80, or I-90, all high-volume truck traffic interstate corridors in our area. Your sedan or SUV may be the same height as the truck’s big tires but it is clear that there is an empty space beneath that trailer loaded with cargo and your vehicle. The variance invites the smaller vehicle to move into that space in the event of a collision, often at great speed and force in a matter of milliseconds.
This has come to be known as an “underride” crash and it can happen when the smaller vehicle slams under the big rig either from the rear or from the side:
- Rear-end underride crash (“full-width”), where the smaller vehicle is forced underneath the back of the truck. This is the most common type of underride accident, and often causes horrific bodily injuries to those victims in the passenger vehicle;
- Side-impact underride crash, where the vehicle is shoved by the collision’s force under the side of the tractor-trailer, also at great likelihood of the passengers suffering shocking bodily harm (like decapitation); and
- Offset underride crashes, where the smaller vehicle slams into the back of the semi-truck but manages to avoid a head-on rear-end collision, hitting the truck corner instead. That heavy corner may pierce the passenger vehicle in the force of impact, causing fatal injuries to the people within it.
For more, including graphics describing these different types of underride accidents, see Data Collection and Reporting of Underride Crashes by Law Enforcement published by NHTSA and Truck Underride Guard Ratings published by the Insurance Institute of Highway Safety.
These serious truck accidents happen much too often, and may be more commonplace than is currently being recognized by regulatory authorities. The National Highway Traffic and Safety Administration (“NHTSA”) reports that underride accidents involving large trucks and passenger vehicles cause around 20% of all truck crash fatalities, while safety authorities like the Truck Safety Coalition confirm that the actual death statistics caused by underride accidents is likely much higher than this estimate “…due to issues with underreporting.” See, Truck Safety Coalition. Underrides Fact Sheet and History. Truck Safety Coalition, 2025.
Regulations to Protect Truck Crash Victims Against Underride Accidents
A few years ago, progress was made in the above-referenced Bipartisan Infrastructure Law when federal regulations were put in place for mandatory guards and markings on commercial trucks involved in interstate commerce to thwart underride fatality risks. Two core protections were made into law in this 2021 legislation:
Today, under the oversight of the Federal Motor Carrier Safety Administration (“FMCSA”), all commercial truck trailers must have rear guards installed on them to block that empty space between the passenger vehicle and the rig.
The federal regulation also demands that the commercial motor vehicle (“CMV”) have its back and sides properly adorned with red and white reflective tape so other drivers can easily see the height and movement of the rig, day or night.
Specifically, for trailers or semitrailers with a minimum weight of 10,000 lbs., 49 CFR §393.86 mandates rear impact guards be installed if they were manufactured on/after Jan 26, 1998. This regulation also incorporates compliance to 49 CFR §571.223 (guard strength) and 49 CFR §571.224 (vehicle-level performance). There are exceptions to the rule, though. Pole trailers, some types of construction trailers, low-chassis vehicles, etc. are not required to install the guards.
Also read: Fatal Truck Crashes: Will Congress Pass the Stop Underrides Act?
Continuing Dangers of Underride Accidents Despite FMCSA Regulation
Sadly, continuing fatal truck crashes are making it clear that more protection is needed to stop the real threat of underride accidents involving 18-wheelers on our roads. Why are there still so many underride accidents involving large trucks with deadly consequences?
Each accident is unique and must be given individual consideration and respect. Generally, the danger of being involved in an underride accident here in Illinois or Indiana involves things like:
- Owner, lessor, or operator of the truck failing to place the guards as required by regulation in the first place;
- Those with possession, custody, or control of the rig (tractor, trailer, etc.) having guards installed but that don’t conform to the regulatory requirements (they are placed too high, for instance, or they are outdated);
- Those with legal duties here not having an effective reflective warning on the sides as mandated by law (the tape is not there; it is peeling; it is not in the proper position; or maybe it’s dirty because no one washed the rig, etc.); and
- Finally, there is no current federal regulation requiring a side guard. The reflectives simply do not offer the same level of protection as a guard installed on the rig. These exist, such as the “Angel Wing Guard” manufactured by AirFlow Deflector, Inc. and approved by the Truck Safety Coalition.
Protecting Against Deadly Underride Accidents
It is well-known among the trucking industry as well as safety organizations and advocates for truck crash victims that the dangers of fatal underride truck crashes remain much too high. Compliance with current regulations is not stringent enough, and more protections (like formal laws mandating side guards as well as rear guards) are not in place.
Nevertheless, nothing prevents those responsible for these CMVs to take measures above and beyond the minimum regulatory standards of 49 CFR §393.86. There is nothing preventing protections being placed on a truck that exceed the requirements of the FMCSA Underride Regulation.
Like what? Fleets and operators could do things like upgrading their guards for higher protection; installing side guards; and even installing front underride guards as suggested by the Truck Safety Coalition. The TSC points out that the National Transportation Safety Board (“NTSB”) has been recommending side, front, and rear underride guards for over a decade.
While these industrial arguments do not meet the compliance requirements of a federal regulation, they do provide support for arguments made by truck crash victims in the aftermath of an underride accident. When civil damage claims are made based upon negligence, product liability, etc., the victim will have the burden of proof to establish legal duties of care were breached which caused them harm. Industrial opinions do have power to support their arguments here that disrespected, known safety measures contributed to their injuries. For more, read Industrial Standards, OSHA Regulations, and Work Accident Injury Claims.
Additionally, fleet owners and operators should be auditing their trailers for compliance and fixing problems; training their truckers on the importance of guards, the risks of underride collisions, the need to keep proper distance between vehicles on the road; and how vigilance is especially important on our hotspot traffic areas like Chicago beltways or Indiana interstates like I-65, I-70, I-69, and I-465. Failures to meet these duties of supervision, maintenance, and oversight may also form the basis of civil liability in the event of an underride crash.
For more, read:
- Truck Crash Injury Claim Evidence: ELDs, EDRs, and FMCSA Regulations to Show Liability
- Expanded Semi-Truck Crash Liability: SCOTUS Rules Freight Brokers Are Liable for Negligent Choices in Transporting Goods
- Chicago Truck Crash Dangers in Neighborhoods and Suburbs
- Huge and Growing Freight Truck Traffic in Northern Indiana: Increasing Danger of Semi-Truck Crashes
- Federal FMCSA Regulations of Commercial Trucking: Impact on Truck Accident Claims.
Underride collisions are often nightmarish where people are horribly injured in preventable accidents when their vehicle is literally rammed under the larger truck body by the force of impact. The risk of these fatal truck crashes is especially great in high truck traffic areas, like our interstates. Please be careful out there!
