Table of Contents
What is Road Restraint System (RRS)?
How to examine the requirement of Road Restraint System
How to decide what type of RRS is required?
What is the need for a terminal at the start or endpoint of a Steel Barrier?
Why Concrete Barrier are Proposed?
You must have noticed Crash barriers or Steel barriers 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.
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.
RRS are expensive assets and also, and 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 streets where vehicular movements are controlled by Traffic Signal Operation, RRS is not warranted in most cases with an exception like significant embankments and proximity of vulnerable poles 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:
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 roads 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 the Length of Need. You can find the detailed Road Restraint System Design Process at gcelab.com online course section.
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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 in adequately delivering the performance of an RRS system.
Transitions are necessary between safety barriers with different Working Widths or containment Levels. They may also be required between barriers and bridge parapets. Transition barriers help to minimise the pocketing effect once an errant vehicle collides with a barrier. A transition barrier in road restraint systems refers to the area where the barrier changes from one type to another. For example, it could be the section where a concrete barrier changes to a steel barrier or where a safety barrier changes from a median barrier to a roadside barrier.
These transition areas can pose a challenge to the effectiveness of the road restraint system, particularly in terms of safety. The transition from one type of barrier to another can create a gap or a change in the height of the barrier, which may increase the risk of a vehicle penetrating the barrier or causing serious damage in the event of a crash. To address this issue, road authorities often use special transition designs and treatments that ensure the continuity and effectiveness of the road restraint system. These transition designs can include flared end treatments, end terminals, or special transition segments that gradually reduce the height or increase the stiffness of the barrier to ensure a smooth transition between different barrier types.
In addition to these design solutions, regular maintenance and inspection of road restraint systems are also essential to ensure that any damage or deterioration is identified and addressed promptly to maintain the safety of the road users.
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:
Placing the concrete barrier along the central median creates visibility obstruction at the curvatures. In that case, widening at the central median is recommended. All above and many more key analyses and assessments are carried out before placing the Road Restraint Systems along the carriageway with adequate setback distance.
I hope this blog helps you to understand and appreciate the hard work of Civil Engineers to make our roads safe and sound for all road users.
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