What Is a Jersey Barrier?

Jersey barriers are dense, strong, specifically engineered concrete blocks used extensively in highway safety. If you’ve driven along a motorway or A-road and seen an interlocking line of concrete barriers forming a blockade between lanes or between the road and the verge, they are almost definitely Jersey barriers.

The primary application is to separate lanes of traffic and stop cars from reaching oncoming vehicles or entering high-risk zones. Jersey barriers are also great for blocking vehicle access to vacant spaces such as sites and car parks.

Designed with a tapered profile, the shape and configuration of each block are essential to the way they function, not simply stopping a moving vehicle due to its weight but redirecting the vehicle to mitigate the potential for serious or even fatal collisions.

How Did Jersey Barriers Get Their Name?

We’ve mentioned the shape of the Jersey barrier – and this isn’t accidental or peripheral to the purpose of the blockade. Jersey barriers were first used in the 1940s and 50s when several notorious roads in California and, unsurprisingly, New Jersey were the locations of multiple severe accidents.

Many of these highways were protected only with wooden rails, which became redundant as cars started to be manufactured with more powerful engines and speed limits increased.

The first use of a concrete barrier was in California, on a road called Dead Man’s Curve, with tight corners and steep slopes responsible for numerous deaths. Those first barriers proved that concrete blocks could reduce the volume of fatalities and were an early incarnation of the road safety measures we see today.

In 1955, New Jersey took the idea and progressed it further, using blocks to prevent avoidable fatalities along a mountain route called US 22. Engineers used trial and error to determine the right shape and structure of the blocks and how their placement affected the outcomes for out-of-control vehicles, increasing the height of the block to similar dimensions still in use now.

How Do Jersey Barriers Stop / Block Fast-Moving Vehicles?

The science and engineering behind a Jersey barrier are the simplicity of a concrete block. These factors help to swiftly reduce the speed of a car, preventing it from causing a head-on crash but also minimising the damage to the vehicle and, therefore, the potential injuries to the driver and passengers.

Incorporating a sloping barrier face means that when a vehicle hits the concrete, the tyres naturally follow forward motion up the surface of the block rather than coming to a dead stop. This movement pattern means the vehicle is forced to spin away from the area of risk – usually a lane of oncoming traffic – and is redirected back in the right direction.

Because the vehicle slides upward along the barrier, rather than crashing directly into it, the wheels bear the brunt of the impact, preventing a vehicle from rolling or the engine block being driven back into the car.

A second, sharper angle above the first part of the barrier causes the bumper to lift while the tyres make solid contact with the slope beneath, slowing the car so the driver can regain control and take over the steering. Raising the vehicle reduces the friction between the pavement or tarmac and the tyres, quickly slowing the car down.

Steve Hardcastle

Head of Sales
Clearway

Steve Hardcastle

Jersey barriers are engineered specifically to redirect moving vehicles rather than simply absorb impact, which significantly reduces the severity of collisions and protects both road users and property.

After years of testing, Jersey barriers have become more widely used as partitions between motorway lanes, to protect highway workers and construction teams close to busy roads, and to redirect traffic during repair work.

Other applications include anti-ram raiding safeguarding systems, with Jersey barriers installed outside high-risk buildings and facilities, on military sites, and in conflict zones where officials must prevent bomb threats and deliberate vehicle collisions.

They’re often used to prevent access to vacant sites and car parks and to control the flow of traffic in a particular space.

How Are Concrete Jersey Barriers Manufactured?

The concrete used in production is incredibly heavy and reinforced with steel bars. Some areas use plastic Jersey barriers, which have a similar function but are intended to be filled with water or sand to mimic the weight and density of concrete.

Hollow plastic Jersey barriers are ballasted – or filled – and can be used in places with vehicle-related risks but with a mitigated potential impact since they are never as heavy as a solid concrete block. The benefit of a hollow Jersey barrier is that the empty units are lightweight and easy to transport, often used on construction sites away from major roads.

Concrete Jersey barriers are highly advisable for any applications where fast-moving cars or vehicles are adjacent to the zone and can be erected quickly using professional vehicles with loading and unloading equipment, positioning and configuring the blocks in any pattern.

Do Jersey Barriers Improve Road Safety?

There is no doubt that a set of Jersey barriers is an investment in safety and security, reducing the prevalence of serious crashes where vehicles become out of control, skid in poor weather conditions, or lose function due to a catastrophic failure.

Rather than sliding into oncoming traffic, hitting a bridge or barrier head-on, or flipping on contact, the car reacts to the angled barrier wall, slowing down and being directed into the correct position.

In the UK, Jersey barriers are used by various authorities, including National Highways, which worked along the M42 near Birmingham for two months in early 2023, fitting 7.5 miles of concrete and steel safety barriers, citing the superior strength of a concrete barricade to reduce collision risks.

Jersey barriers are essentially maintenance-free and last double the lifespan of a metal barrier exposed to rust and corrosion, which can reduce the effectiveness of the traffic control measure.

As the debate around smart motorways rumbles on, it’s expected to see more Jersey barriers used as the safety measure standard in British roadways, where the government has committed to adding concrete barriers to every motorway without a permanent hard shoulder.

For more information about Jersey barriers, how they may be relevant for your construction site, roadway project or development, and independent advice about the right concrete barrier block sizes, weights and configuration, please get in touch with the Clearway team at your convenience.

Written by Steve Hardcastle

Chief Technical Officer

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Steve Hardcastle is Chief Technical Officer at Clearway, bringing extensive leadership experience from across the security sector, including the management of NSI and ACS-accredited businesses and the founding of Cerberus Security and Monitoring, which he led for over 25 years.

Working closely with Clearway’s research and development team, Steve helps shape the Group’s technical direction by identifying innovative technologies that enhance service capability, support operational performance, and provide a competitive advantage. His role includes developing technology strategies that support business growth, while also strengthening and evolving the Group’s existing product range.

Steve also provides technical and practical support across the wider business, working with sales, marketing, and operational teams on solution design, product positioning, implementation challenges, and day-to-day technical issues. His broad industry knowledge and hands-on approach play an important role in ensuring Clearway remains at the forefront of security technology and service innovation.