Vehicle impact protective devices S-rated for low-speed traffic
Bollards are often used to harden a perimeter against vehicle incursion, protecting the area behind them from accident or attack, along with other types of barriers or site furniture. All crash barriers are not the same, however: their stopping power depends on both their construction and installation.
As site designers look at creating protected areas, they must consider what sort of vehicle incident they are trying to mitigate. A fast food restaurant with a drive-thru window might install crash protection bollards to help prevent cars from misjudging distance and rubbing against the wall. This bollard will deal with slow moving cars nudging past it: the threat that a car will drive nose-first into the post at high speed is very low. In comparison, governmental buildings or other official sites have a much higher threat risk. Perimeter security measures may need to stand up to concerted attack, adding crash barrier posts that can take head-on, intentional collision. Those sites that have longer unprotected roadways leading in a straight line to the walls may be more vulnerable than those that are nestled in a zig-zag of obstacles that would prevent a vehicle from getting to highway speeds.
The threat level at a site, then, is based on how likely it is to be targeted, the geography and placement of the location, and its overall structural vulnerability. This threat level will dictate the kinetic force a barrier must resist to provide a safety or security benefit. Crash ratings allow manufacturers and site designers to easily note what level of force a barrier can handle.
A brief history of barrier crash ratings
In 1985, the US Department of State released a system to rate barriers and gates against vehicle crashes in a test standard called SD-STD-02.01 Test Method for Vehicle Crash Testing of Perimeter Barriers and Gates. This standard was used mostly internally until 9/11, when renewed interest in protecting against terror attack put perimeter defense on everyone’s mind.
The 1985 specification still forms the basis of impact barrier crash testing today. The original tests were all done with medium-duty truck. It would be driven into the barrier, head on, and the tester would measure how far the truck’s flatbed penetrated past the barrier.
If the penetration was less than or equal to:
- 3.3 ft: L3.0 Penetration Rating
- 20 ft: L2.0 Penetration Rating
- 50 ft: L1.0 Penetration Rating
- > 50 ft: Failure
This barrier could be tested at different speeds. The faster the speed of the oncoming vehicle, the higher the kinetic energy. Tested speeds with the medium duty truck were 30, 40, and 50 mph.
After 9/11, this methodology evolved into the Department of State’s kinetic-energy based K-rating, released in spring 2003. These K-ratings had a much more rigorous requirement: the test vehicle was not crash rated if it penetrated any farther than 3.3 feet past the barrier.
It wasn’t just military and governments considering the crash-perimeters around their sites. As private interest in K-rated vehicle barriers grew, the American Society for Testing and Materials (ASTM), a non-governmental standards organization, began the process of creating rigorous testing standards. They added a variety of vehicle classes, including passenger car and heavy truck categories.
Vehicle impact bollards and the city street
Although these original ASTM rated bollards are incredibly important for sites with a higher threat level, changing traffic patterns have seen an increase in need for lower-impact barriers.
Across the US, there are 60 crashes per day into convenience stores, homes, and other buildings—most of which are low-speed accidents. Distracted driving, driving under the influence, traffic accidents, and pedal errors make up most of the incidents.
After years of downward trends, the United States has seen a jump in traffic fatalities: a 13.5% increase from 2010 to 2016. This is attributed to more crowding on the streets and an increase in distracted driving. Young drivers, between 19 and 24, are particularly distracted by technology. Additional trends are developing as the Baby Boom ages, increasing percentage of drivers on the road have their 65th birthdays. Those under the age of 20 and over the age of 65 are more prone to pedal errors.
An environment of distraction and collision means barriers are often installed as a safety device, rather than providing hardened security. Even in these safety situations, like protecting a storefront from a driver accidentally hitting the gas as they pull into a parking spot, the vehicle impact bollard must be able to absorb kinetic energy. Yet it does not need the engineered stopping power that can halt a heavy-duty truck going at highway speeds. For this reason, the ASTM has recently introduced “low-impact” testing standards for vehicle impact protective devices, so that facilities executives and engineers can choose a lower impact bollard that best fits traffic conditions and threat level.
Low-impact ASTM crash ratings
In 2014, ASTM added standard F3016 / F3016M – 14: Standard Test Method for Surrogate Testing of Vehicle Impact Protective Devices at Low Speeds to answers the need to specify the kinetic stopping power of lower impact crash barrier posts.
The crash ratings for this standard are as follows:
|ASTM Standard F3016/F3016M for Surrogate Testing of Protective Devices at Low Speeds
(with specified crumple zone)
|S10–10 mph S20–20 mph S30–30 mph
|P1 ≤ 1 ft P2 1–4 ft Failure ≥ 4 ft
This test is done with a “surrogate” vehicle, constructed with a crumple zone in the nose. Because of this test-specific vehicle, and because vehicles to be tested will be moving more slowly, the penetration ratings are substantially shorter than those for vehicles with higher kinetic potential. As a lot of the interest in these tests are coming from storefronts, utilities companies who need to protect meters or boxes, and other sites that do not have room for large perimeter set-backs, the smaller penetration distance is of vital importance.
What are the ASTM F3016 test methods?
In the ASTM F3016 test, a surrogate vehicle is built to specification, with a designed crumple zone in the nose. It must weigh 5000lbs +/- 110 lbs. When being tested, it must strike the protective barrier at 28 in +/- 1 in, head on, at 90° +/- 1.5°.
There are two designations in the specification, for rigid and shallow mount devices. Rigid devices are placed in washed sand, whereas shallow mount devices are fixed to a mount that is no deeper than 12in below grade. This detail is important, as the depth of a specified footing helps provide some of its crash protection.
This summary of the ASTM test method does not provide the full specification but provides insight for those looking for low-impact crash rated bollards who wish to know what the ratings mean.
Vehicle impact safety in low-threat situations
As site designers including architects, city planners, facilities executives, landscape architects, and contractors become increasingly aware of perimeter planning for security and safety, it is wise to get to know and understand the various standards determining the crash-ratings of bollards and other site furnishings. Low-impact ASTM ratings fill a gap in crash-rating specification, an adjunct to tests dealing with the kinetic energy of larger vehicles and higher speeds. Although every scenario does not need a crash-tested bollard, these low speed ratings help define what sorts of forces might impact a safety bollard in a low-threat situation.