Unless you’ve been in a vehicular accident (which I hope you haven’t), you won’t notice how much road barriers have evolved over the years.

Despite what you see on television, these accident prevention materials have actually gotten better at saving lives rather than ending them. It just so happens that the small percentage of deaths related to them are the ones that always make the news.

YouTube video

In this informative video by Andrew Lam, he mentioned how Americans have the Manual for Assessing Safety Hardware (MASH) to thank for that.

To put it simply, MASH is a strict set of guidelines that manufacturing companies have to adhere to when making roadside safety equipment. The guidelines are constantly being updated to cover more equipment and the ever-increasing types of vehicles on the road.

There is a LOT of road safety equipment out there but Andrew focuses on road barriers and how they have become safer, thanks to MASH.

road barrier safety design

Road barriers have three general rules to follow:

  1. They have to keep vehicles upright and not cause them to roll over.
  2. They should not cause vehicles to tip more than 75° or go over the barrier.
  3. They should not be able to penetrate or crush the passenger compartment.

There’s a lot more information regarding each rule, but that’s the gist of it. To prevent vehicles from crashing into obstacles or going off the road, the road barriers themselves have to be safe to crash into.

There are three types of road barriers: concrete, guardrail, and cable. Different road barriers are used on different roads depending on factors such as traffic, type of vehicle frequency, and your local government’s funding.

road barrier safety design

Concrete barriers are the most solid and expensive. They have a sloped surface that, if properly designed like the F-shape and single slope barriers, can bounce a vehicle off its surface without launching it skyward. This slows down the vehicle and prevents it from hitting anything else at a high speed.

You’ll commonly find concrete barriers in enclosed areas that have hazards – like on the edges of flyovers or near construction sites.

road barrier safety design

Where there is more space, guardrails can be implemented. In contrast to concrete, guardrails have a rather ingenious design. The rails are held via posts that are placed into the ground. When hit, the rails push the posts outward and into the ground, using the soil as a cushion. The soil then absorbs the kinetic energy, slowing down the vehicle.

road barrier safety design

When guardrails are connected to something more solid (like a concrete wall), more posts are placed near the material to prevent the guardrail from tearing. Without these extra posts, the broken guardrail will allow vehicles to smash directly into the solid material – and nobody wants that.

road barrier safety design

Lastly, you have cable barriers. These are the cheapest barriers available and use three to four cables to mitigate the damage from a vehicle crash. A lot of controversy surrounds these cable barriers since their high penetration rate and low cost makes them less preferable to concrete or guardrails.

road barrier safety design

Provided the barrier is of the guardrail or cable variety, you’re bound to find a terminal grounding it. This has also seen design changes over the years and are now way safer to hit, should you find yourself accidentally barrelling towards one. One type of terminal collapses into the barrier if you hit it head-on, while another pushes itself under the vehicle which mitigates frontal damage.

road barrier safety design

You also have crash cushions, which serve a similar purpose to terminals but are placed in front of more solid structures like concrete barriers or toll booths. These include sacrificial systems like sand barriers and cushions which use polyurethane cylinders or gas.

The whole video is definitely worth a watch, as Andrew explains more about these systems and how your government determines just how much your life is worth when investing in these road barriers.


Carlos wrestles gators, and by gators, we mean words. He also loves good design, good books, and good coffee.