If you’ve ever been on a highway at rush hour, you’ve probably stared ahead at the concrete or metal barriers lining the road and thought little of them—until that one time a car swerved out of a lane too close, and you realized how those unassuming structures were keeping you safe. As a traffic barrier supplier with over a decade in this industry, I get asked this question all the time: how do these barriers actually stop side-swipe collisions? It’s not just about being a solid wall. There’s a lot of science, testing, and real-world design that goes into every barrier we ship, and today I want to break that down in plain terms, no overly complicated jargon, just what I’ve learned from working with contractors, state DOT teams, and seeing the data from accidents they prevent. Traffic Barrier
Let’s start with what a side-swipe collision actually is, because if you don’t understand the problem, you can’t understand how barriers fix it. Side-swipe crashes happen when two vehicles traveling on the same plane (same road, same general direction) come into contact along their sides, not front or back. Most often, this is a single vehicle first, right? A driver glances at their phone for two seconds, drifts over 12 or 18 inches, and hits the lane line, the rumble strip, or something worse: the edge of the road, an embankment, or another car in an adjacent lane. The National Highway Traffic Safety Administration (NHTSA) has data that side-swipe crashes make up about 15% of all highway crashes, and almost 30% of crashes on rural roads—ways where lane widths are narrower, or shoulders are more uneven. What people don’t realize is that side-swipe collisions aren’t just fender benders. They can cause vehicles to spin out, cross into oncoming traffic, or go over a steep embankment, leading to far more serious crashes than the initial side impact.
That’s where traffic barriers come in, but not all barriers do the same job. When we’re designing for side-swipe prevention, we’re not just talking about the tall concrete dividers you see on interstates—though those are part of it. We make a range of barriers, from flexible steel beam barriers for rural roads to modular concrete barriers for urban construction zones, and each is engineered to address different types of side-swipe risks. Let’s walk through how each works, starting with the basics of barrier energy absorption.
First, side-swipe collisions exert a specific type of force on a barrier: a lateral, sideways push, not a head-on impact. Good barriers don’t resist that force rigidly—rigidity can cause a vehicle to bounce back into traffic, which is another crash hazard. Instead, modern barriers are designed to dissipate that energy gradually, over time and distance, so the vehicle slows down without spinning out. For example, our standard steel beam guardrail barriers (the ones you see along most two-lane rural roads) are made of three 12-foot sections of galvanized steel, connected by heavy-duty splice plates. When a car swipes the side of the beam, the beam doesn’t just stay straight. The splice plates flex, and the steel beams deform along the length of the crash, not just at the point of impact. NHTSA’s Manual for Assessing Safety Hardware (MASH) requires these barriers to withstand a 2,000-pound vehicle traveling at 60 mph hitting them at a 25-degree angle, which is exactly the angle most side-swipe crashes happen. That’s not a random test—25 degrees is the typical angle a drifting car makes when it touches the edge of a lane, so the barrier is built to catch that impact before the driver can overcorrect and lose control.
Wait, but what about the barriers that line the edge of the road, not between two lanes? A lot of side-swipe crashes happen when a car drifts off the paved road, not into another lane. For those, we have what’s called “end treatment” for barriers, which is a key part of side-swipe prevention that most people don’t notice. If a standard steel barrier just ended abruptly at the edge of the road, a car that drifts off would hit that sharp end, which is a major hazard. Instead, we design the ends of our barriers to “break away” gradually. The end piece is a curved, tapered steel section that the car’s bumper catches first. Instead of penetrating the car or bouncing it back, the end peels back, and the main barrier section flexes, absorbing the force as the car slows down. We tested this last year with a state DOT in Ohio: they had a 10-mile stretch of two-lane road where side-swipe crashes off the road made up 40% of their total crashes. After installing our tapered end barriers, they reported a 72% drop in those types of crashes in the first year, and that lined up with our own internal crash data from similar projects across the Midwest.
Now, the barriers that are between lanes, called median barriers, are a whole different category of side-swipe prevention. On highways, medians are often narrow, so a side-swipe crash in one lane can send a car straight into the opposite lane, or into the median itself. Our modular concrete median barriers (the ones you see with the tapered top that’s yellowed or painted white) are engineered for two specific jobs: first, to prevent side-swipe crashes from crossing the median into oncoming traffic, and second, to contain a vehicle that has already drifted. What’s clever about these barriers is their shape: the sloped top face. When a car hits the side of the barrier at an angle (the same 25-degree side-swipe angle), instead of the car digging into the concrete and flipping over, the sloped face guides the vehicle back onto the road, at a controlled angle. MASH testing for these barriers requires them to stop a 5,000-pound SUV traveling at 70 mph, which is exactly the speed of highway traffic where side-swipe median crashes are most deadly. We worked on a project in Texas a few years ago where a driver fell asleep at the wheel, drifted across three lanes, and hit our median barrier. The sloped face guided their SUV back into their lane, and they only had minor injuries—no crash with oncoming traffic, no rollover. That’s the kind of outcome we design for every day.
Another big part of side-swipe prevention that I don’t see talked about enough is barrier placement and height. A lot of people assume barriers have to be six feet tall to work, but for side-swipe crashes, height is tailored to the average vehicle’s bumper height. Most passenger cars have a front bumper height between 16 and 20 inches, while SUVs and pickup trucks are between 20 and 28 inches. Our steel beam barriers are set 27 inches above the road surface, which means the bumper of any common vehicle will hit the beam, not the space below it where the barrier could catch a tire and cause a roll. For concrete barriers, we adjust the height slightly based on the road’s typical traffic mix—if a road has a lot of large trucks, we make the barrier 30 inches tall to make sure the truck’s frame catches it, not the bumper. That small adjustment is the difference between a side-swipe that stops the car and one where the tire snags, leading to a rollover.
I also want to address a common misconception: traffic barriers don’t just “block” side-swipe crashes—they reduce the risk from the moment a driver starts to drift. How? Visibility. All of our barriers come with highly reflective sheeting, or are painted with high-visibility yellow or white, so a driver can see the barrier ahead even in rain, fog, or at night. That visual cue is a huge part of side-swipe prevention in itself. When a driver sees the barrier line at the edge of the road or between lanes, they correct their drift before it becomes a crash. A study from the Federal Highway Administration (FHWA) found that roads with properly marked and placed barriers have 40% fewer lane departure events, which are the precursors to side-swipe crashes. That’s not just from the barrier catching a crash—it’s from the barrier acting as a visual reminder to stay in your lane.
But here’s the thing: barriers aren’t one-size-fits-all, and that’s why our team works closely with every customer to match the right barrier to their specific side-swipe risks. For example, a urban construction zone has short travel distances, mixed small and large vehicles, and higher traffic speed, so we recommend temporary modular barriers that are easy to move but still meet MASH standards. A rural two-lane road with narrow shoulders has higher risk of drivers drifting off the road, so we recommend barriers with tapered ends and flexible steel beams that can handle the softer shoulder terrain. A wide highway median with low crash risk might use a lower, lighter barrier, while a narrow median on a busy interstate uses a heavier concrete barrier to prevent cross-over crashes.
I’ve seen too many project teams try to cut corners on barrier selection, and it always leads to more side-swipe crashes. Last year, I spoke to a DOT in a southern state that installed cheap, untested barriers on a stretch of road that had a history of side-swipe crashes off the shoulder. Six months later, there were three crashes where cars hit the barriers, bounced back into traffic, and caused multiple-vehicle collisions. They ended up replacing the barriers with our tested, flexible steel beam barriers, and over the next 18 months, those bounce-back crashes dropped to zero. That’s the real-world proof of how barrier design matters for side-swipe prevention.
Now, I know a lot of people hear “side-swipe collisions” and think about minor fender damage, but the reality is that these crashes are responsible for thousands of injuries and fatalities every year. NHTSA reports that over 900 people die in side-swipe crashes annually, and millions more are injured. Traffic barriers are one of the most cost-effective safety tools on our roads—every dollar spent on high-quality, properly installed barriers saves an estimated $8 in crash-related costs, according to FHWA data. But only if they’re designed and installed for their specific purpose.
As a traffic barrier supplier, this is what drives me: every barrier we ship isn’t just metal or concrete. It’s a part of a system that keeps families safe on their commute, keeps truck drivers from losing control of their rigs, prevents the kind of crashes that turn a routine drive into a tragedy. We don’t sell barriers as a one-size-fits-all product, because side-swipe risks aren’t one-size-fits-all either.
If you’re working on a road project, whether it’s a highway expansion, a rural road upgrade, or an urban construction zone, and you need guidance on which barriers will best prevent side-swipe collisions, our team is here to help. We can share our real-world crash data, walk you through MASH testing requirements, and work with you to design a solution that fits your specific project needs. Reach out to our team to discuss your traffic safety goals, and we’ll provide a tailored, cost-effective solution that meets and exceeds safety standards.
Concrete Railing References:
National Highway Traffic Safety Administration. (2022). Traffic Safety Facts: Crash Data Overview. U.S. Department of Transportation.
Federal Highway Administration. (2021). Manual for Assessing Safety Hardware (MASH) Compliance Guidelines. U.S. Department of Transportation.
Federal Highway Administration. (2020). Cost-Benefit Analysis of Roadside Safety Barriers. U.S. Department of Transportation.
Ohio Department of Transportation. (2023). Rural Road Side-Swipe Crash Reduction Project: Final Report. Ohio DOT.
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