Crash Rated Barriers
Photo by Nick Fewings on Unsplash
Those among us who have had exposure to crash rated barriers would have come across several terms such as K rating, M rating and KW rating. There is an interesting history behind crash rated barriers, and how their standards developed.
October 1983. Beirut, Lebanon. Two suicide bombers drove two heavy-duty trucks containing bombs into the military compound at Beirut airport. The bombs were detonated near barracks filled with French and American soldiers. 305 military and civil personnel were killed - the worst single-day loss for both the American and French military.
After this incident, the US government realized how vulnerable their buildings and facilities were to such threats. It became obvious that they need some security barrier to protect their facilities from heavy vehicles. Different barrier systems were developed by various government agencies. But each of them had different testing parameters and a product developed by one agency did not pass the tests of another. There needed to be some standardization in the method of testing and that's how the testing standards developed by the Department of State, SD-STD-02.01 became the universally accepted testing standard in the United States.
We may have come across articles and posts about security being upgraded in major Indian cities and buildings after the 26/11 attack in Mumbai. Along with other security measures like SWAT teams, the government also improved the security level of building with the help of barriers and bollards. We might have also heard about how bollards were installed around Taj Mahal to bring increased security and traffic control to the area. Automatic barriers and rising bollards were installed around the monument to prevent vehicles from crashing into the gates. But, how did they know which barrier to choosing for each of these applications? This is where the testing standards developed by the American Department of State (DoS) helped.
Let's now look at the different ratings developed and pick the right crash-rated barrier for our application.
The first system for crash-rated barriers was the K ratings. It was developed by the DoS based on the distance a 15000lb vehicle's front bumper went past the barrier. K rating can be thought of as how easily the barrier can stop a vehicle of weight 15,000lb moving at different speeds. Three different ratings are there-
In addition to the weight of the vehicle, K rating also takes its speed into account.
Penetration rating gives us an idea of how far a vehicle will move after hitting the barrier. Penetration is measured using three categories (called L rating).
L1 - 20 to 50 ft
L2 - 3 to 20 ft
L3 - 3ft or less
The shorter the penetrating distance, the better is the barrier's performance. The L rating was designed based on the security level a facility needed. L3 sites were heavily guarded areas and thus barriers with L3 rating meant that it stopped the vehicle with less than 3ft of penetration.
K12 rated bollards can be seen in high-security areas like airports, embassies, and banks.
Soon, the DoS standard was used by engineers and architects for commercial buildings as well. People started realizing how these barriers can be used to prevent ram-raiding. Shopkeepers started installing bollards and barriers in front of their shops and architects included bollards in their buildings as a measure against ram-raiding and protecting buildings from accidents.
That's how ASTM International (American Society for Testing and Materials) took over the DoS and introduced another rating, M rating.
How is K rating different from M rating?
M rating is very similar to the K rating except for the penetration rating. L rating was replaced by P rating in which the vehicle's penetration was measured as-
P1 - less than or equal to 1m
P2 - 1.01 to 7m
P3 - 7.01 to 30m
P4 - greater than or equal to 30m
The speed and weight of the vehicle were kept the same. ASTM standards are available for both high-speed and low-speed crashes. Low-speed crash standards are commonly referred to as the ASTM F306/F3016M rating.
Ratings for vehicles with different weights such as small passenger cars, medium-duty trucks, pickup trucks, and heavy goods vehicles are available.
Where are ASTM rated bollards used?
ASTM-rated bollards and barriers are used in front of buildings and shops. They help in preventing grab-and-run robberies and also to minimize damage to buildings due to accidents. Very often accidents cause vehicles to steer away from the roads and ram into shops. The same thing can happen in our warehouses or factories where forklifts and similar vehicles are used to transport goods. Loss of property due to accidents can be easily controlled by installing barriers of appropriate ratings.
Finally, there's another type of rating given by ASTM called the WK rating. It addresses errant vehicles and is mostly used to rate items like barriers, gates, planters, and bollards. It focuses on low-speed vehicles.
Anti-Ram VS Crash Attenuation
Standards to alleviate vehicle impact were also introduced. They are mostly used while building barriers on highways. Accidents on highways are very common. People lose control over their vehicles and collide with others or roll down steep slopes. Guard rails and metal crash barriers must be tested and proven safe so that they can be installed in such dangerous places to avoid loss of life.
These barriers, also called crash attenuators, help in reducing the damage caused by accidents. They slow down or cushion the vehicle. NCHRP standards are commonly used standards in highway barriers. MASH standards were also developed based on the weight of the vehicle.
How exactly do these standards help us in choosing the barrier us want?
Firstly, knowing the penetration rating will help us in selecting an appropriate barrier for specific site conditions in our facility. Once we have a vague understanding of the type of barrier we want, we can get it tested for the site conditions in our facility.
Next, these rating systems can also be used to extrapolate results to other rating systems. For example, the PAS 68 rates barriers on the basis of vehicle and pendulum impact. By comparing PAS standard vehicle weight with that of ASTM standards, we will be able to be a better judge while choosing between two barriers that have different ratings.
While picking a barrier system lookout for certain crash terminologies, some of which are very misleading.
Tested - barriers labelled tested only mean that they were testing using the standards. They may not have passed the test. Products that have passed the tests will have detailed test reports.
Rated - the barrier is tested on the basis of the mentioned standard by an accredited agency and passed the test.
Engineered - the product was engineered with respect to the designs provided by a standard but has not been physically tested.
Equivalent - since M and K ratings are similar, an M50 certified product can be used instead of a K12 certified product and give the same results.
Remember to assess the environment and the site before placing a barrier. It is recommended to get experts to help us choose the right barrier system.
Written by Haritha S.