Why Road Restraint System is so Important – 5 Key Points

By August 28, 2020March 12th, 2021Civil Engineering, Highway Engineering
Road Restraint System

You must have noticed Crash Barrier or Steel Barrier along the high-speed motorways or national road, but do you know why a road restraint system is so important for our modern motorways?

Please read this blog for details.

What is Road Restraint System (RRS)?

Road Restraint Systems (RRS) are an indispensable element of modern road infrastructure and establish as one of the most important life-saving devices.

Road Restraint Systems can also provide the indirect benefit of protection for road workers at places of frequent maintenance intervention where temporary working methods would otherwise require the installation of physical barriers.

How to examine the requirement of Road Restraint System

RRS are expensive assets and also, they need regular maintenance every time they are hit by a vehicle and dislodged moderately or significantly.  So, It’s very important to understand when you actually need a road restraint system. For low-speed urban street where vehicular movements are controlled by Traffic Signal Operation, RRS is not warranted in most of the cases with an exception like significant embankment and proximity of vulnerable pole from the road edge, etc.

The requirement of the road restraint system comes from a comprehensive RRS appraisal process. The key stages of the appraisal process are as below:

Identify the Issue > Assess the Risk > Risk Reduction > RRS Design

In a simple word, one must identify the issue first. Once you know the issue, assess the risk associated with that issue. Once you know the risk associated with that issue, find the solution to mitigate the risk or eliminate the risk. if the mitigation or elimination process recommends providing an RRS system then start to design the Road Restraint System.

In the UK, the Road Restraint Risk Assessment Process (RRRAP) is carried out through a software-driven process and it has two main elements:

  • Risk Analysis, and
  • Risk Assessment

blog risk assessment 01

How to decide what type of RRS is required?

Once the appraisal process recommends providing RRS along the project road, it’s time to decide what type of RRS system to be placed. The selection of RRS depends on the following key parameters:

Containment Level – For high-speed road with limited working width, it is recommended to provide a high containment level. It helps in absorbing the impact with a minimum deflection from its original position.

Available Working Width- Working width is the maximum deflection of RRS from its original position when the vehicle hits the RRS.

Set back Distances – Setback distance is the distance of RRS from the face from the edge of the carriageway.

Length of Need – When there are multiple hazards are placed along the carriageways, then it is required to place a continuous RRS and terminals at both ends. The minimum length of the required RRS is known as Length of Need.

You can find the detailed Road Restraint System Design Process at gcelab.com online course section. Please click here to see the course details.

Also, see the link of a free view of the course module:

What is the need for a terminal at the start or endpoint of a Steel Barrier?

Terminals are provided to absorb the direct impact on a vehicle in case a vehicle leaves the collide with the front face of the barrier. Terminals play a very important role to adequately deliver the performance of an RRS system.

What is Transition Barrier?

Transitions are necessary between safety barriers with different Working Widths or containment Levels. They may also be required between barriers and bridge parapets. Transition barrier help to minimise the pocketing effect once an errant vehicle collides with a barrier.

Why Concrete Barrier are Proposed?

Concrete Barriers are provided along the central median and it comes with a number of advantages and so they are widely accepted across the globe:

  • Virtually maintenance-free for a long period
  • Remain functional even after severe collisions
  • Very High Containment Level
  • Zero Working Width Needed

Placing the concrete barrier along the central median creates the visibility obstruction at the curvatures. In that case, widening at the central median is recommended.

All above and many more key analysis and assessments are carried out before placing the Road Restraint Systems along the carriageway with adequate set back distance.

I hope this blog helps you to understand and appreciate the hard work of Civil Engineers to make our road safe and sound for all road users.


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