August 30, 2002
Mr. Rodney A. Boyd
Trinity Highway Safety Products Division
Dallas, Texas 75356-9619
Dear Mr. Boyd:
In his June 5 letter to Mr. Richard Powers of my staff, Mr. Don Johnson requested Federal Highway Administration review and acceptance of a device named the Collision Performance Side Impact (CPSI) intended for use as a modification to energy-absorbing w-beam guardrail terminals like the ET-2000, specifically to improve its side impact performance. The CPSI is manufactured from 10-gauge steel with 6-mm interior "wings" as shown in Enclosure 1A. Enclosure 1B shows its installation on an ET-2000.
The CPSI was installed on the impact face of an ET-2000 and struck with an 820-kg car propelled sideways at 50 km/h. The impact point was at the driver's door. As shown on the enclosed test summary sheet (Enclosure 2), maximum passenger compartment intrusion was 104 mm, occupant impact velocity was 5.8 m/sec and the 10-millisecond ridedown accelerations were 7.1 g's. Approximately 1.7 m of w-beam was extruded in the crash. Although no baseline test was run on a standard ET-2000, side impact tests at the same speed have been conducted previously on flared terminals such as the BCT and the MELT, with significantly greater penetrations into the passenger compartment.
While the CPSI cannot be considered a safety device on its own, it will not likely degrade the performance of any approved energy-absorbing terminal to which it is attached and it can reduce the severity of certain types of impacts as demonstrated in the crash test. It is therefore acceptable for use as an add-on or retrofit to the ET-2000 and other types of energy-absorbing w-beam terminals at the discretion of the appropriate transportation authority and with the permission of the terminal manufacturer.
(original signed by Carol H. Jacoby)
Carol H. Jacoby, P.E.
Director, Office of Safety Design