Highway Guardrail: What Is Its Purpose?

Have you ever wondered what highway guardrails are doing? The main purpose of a highway guardrail is to form a safety barrier to help protect motorists who bear off the road.

If a car goes off the road , the best thing that can happen is for that car to come to an unimpeded stop. However, that's not possible sometimes. In some parts of any stretch of road, there may be steep embankments, side slopes, or even trees alongside the road. Other obstacles such as utility poles, bridge abutments, and retaining walls, it's much better to hit a guardrail than an obstacle, which is why our guardrails are usually installed.

Highway guardrails mitigate the severity of potential crashes and make roads safer. Guardrails can work in a myriad of ways, from deflecting a vehicle back onto the road, slowing or stopping it, or in some cases just slowing it down enough to get it through the guardrail.

Guardrails aren't 100% insurance, but they do help. Obviously, the size of the vehicle and the speed at which it hits the highway guardrail play a role in the effectiveness of the guardrail in slowing down the vehicle.

Before installing a guardrail, engineers weigh all potential factors to ensure that the guardrail will work properly in all conditions. Guardrail is a complete system in itself, not just a separate component. As part of the whole, each part serves a different purpose. Everything from the posts that are driven into the ground to the way the guardrail connects to the posts is important.

The terminals and the anchoring systems at the terminals are important. But overall, a highway guardrail basically consists of two key parts: the guardrail and the end terminal.

1. The front of the guardrail is, as its name suggests, the part that runs along the road from the end. Its function is simple and always the same to allow vehicles that hit it to rejoin the road.

2. The terminal end is the starting and ending point of the guardrail. The terminal requires some sort of energy-absorbing treatment as the impact from the vehicle is absorbed and then slides down the track. Terminals work in two ways: if a vehicle collides head-on, the impact head slides down the guardrail and away from the vehicle until the energy from the impact dissipates and the vehicle comes to a stop. When a vehicle impacts at an angle, the impact head may push the guardrail or gate out, allowing the vehicle to pass behind the guardrail. So in this case, the guardrail is pushed through, much like the action of a door opening.

Guardrail systems are always tested for performance before they are actually installed on the road. The performance of the system is evaluated through crash tests conducted in a controlled environment.

Certain criteria are used by safety professionals to determine if the system meets standards.Guardrail frontal testing is used to determine if a vehicle will be guided back onto the road when it encounters a guardrail.

The end terminal test is then performed with a frontal and angled vehicle impact. This will determine if the system will properly absorb the energy from the vehicle.

For frontal impacts, the energy absorbing end should absorb most of the energy, allowing the guardrail to gate or extrude and the vehicle to pass through. This will allow the vehicle to slow down after passing through the guardrail, bringing it to a stop with minimal damage.

Tests used to test guardrail systems are typically conducted at 60 mph, so it's important to understand that if a vehicle hits a guardrail at a higher speed, the system may not function properly.

Highway driving are especially problematic because the guardrail system simply can't accommodate vehicles that are well over the speed limit. The faster the vehicle is travelling when it hits the guardrail, the more damage it may cause, as the energy displayed is much greater. Even a guardrail system operating at peak performance can only absorb so much energy.