Barriers are certified by crash testing full-scale prototypes at one of
a handful of authorized test facilities in the U.S. The U.S. Department of State (DOS) released
the first vehicle barrier certification standard in 1985. They created the standard because many
embassies were in historic buildings built close to the streets, and thus
were susceptible to vehicle-based attack.
That standard used a medium-duty commercial truck loaded to a total
weight of 15,000 pounds and crash tested at 30, 40, or 50 miles per hour
(mph). Based on how far the vehicle
penetrated beyond the impact point, the barrier received a letter and number
rating as follows:
U.S. Department of State 1985 Barrier Certification Standard
Speed at Impact |
Speed Rating |
Penetration Distance |
Penetration Rating |
30 mph |
K4 |
< 3 ft |
L3 |
40 mph |
K8 |
3 - 20 ft |
L2 |
50 mph |
K12 |
20 - 50 ft |
L1 |
For example, if a barrier stopped a 15,000-pound truck traveling at 40 mph and the truck penetrated six feet beyond the impact point, the barrier received a K8/L2 rating.
The standard was tightened in 2003 when the DOS decided that any vehicle
that penetrated more than 3 ft. would fail certification, thus the “L” ratings
for penetration distance was eliminated and only the “K” ratings remained. This was a disservice to users of portable
barriers. Those barriers dissipate the
vehicle’s impact energy by sliding along the ground, thus they could no longer be
certified.
Recently ASTM International, formerly the American
Society for Testing and Materials, has taken on the responsibility for
vehicle barrier certification standards. They kept essentially the same rating
designation as the DOS, but added several more vehicle weight (mass) and speed
categories, and also reincorporated the penetration distance allowances.
It is important to recognize that both the DOS and the newer ASTM
standards are based on a vehicle’s kinetic energy (hence the “K” rating in the
original 1985 standard). Kinetic energy = ½MV2 so a vehicle’s speed is the dominant factor in determining its impact energy. The following vehicles traveling at the listed speeds all have about the
same kinetic energy:
Vehicle Type |
Vehicle Weight
(pounds) |
Vehicle Speed (mph) |
car
|
2,400 |
125 |
light truck |
5,100 |
85 |
medium truck |
15,000 |
50 |
heavy truck |
65,000 |
25 |
locomotive |
200,000 |
15 |
train |
10,000,000 |
2 |
Thus, any barrier that is rated K12 (DOS
standard) or M50 (the equivalent ASTM standard) is capable of stopping any of
the above vehicles traveling at the listed speed. And if some amount of penetration distance is
acceptable, then the K12 (M50) barrier can stop the above vehicles even
if they are traveling at higher speeds.
|
|
The certification
crash test of our
Arrestor model
barrier |
Because conducting a full-scale crash test of a
new barrier is so expensive, some barriers are rated to an ASTM or DOS standard rather than certified to that standard.
This means that the designers have calculated the barrier's capability
based on previous experience and tests, but have chosen to forego the actual
crash test. PRO Barrier Engineering’s LightFoot
barrier is a rated barrier. Its design
is based on the Arrestor barrier (which is certified K12) but it is
rated at K4 because it has less energy absorbing material and a shallower foundation
depth.
A big disadvantage to a certified barrier is
that once certified, the design cannot be improved and retain its certification
without conducting another full-scale crash test. In contrast, rating a barrier allows us to continuously
improve the design without having to pass along the expense of additional crash
tests to our customers.
Contact Us if you would like further information regarding vehicle barrier
certification and the newest ASTM crash test standard or return to FAQs.