Carolyn E. Hampton

Crash Severity: A Comparison of Event Data Recorder Measurements with Accident Reconstruction Estimates

The primary description of crash severity in most accident databases is vehicle delta-V. Delta-V has been traditionally estimated through accident reconstruction techniques using computer codes, e.g. Crash3 and WinSmash. Unfortunately, delta-V is notoriously difficult to estimate in many types of collisions including sideswipes, collisions with narrow objects, angled side impacts, and rollovers. Indeed, approximately 40% of all delta-V estimates for inspected vehicles in the National Automotive Sampling System / Crashworthiness Data System (NASS/CDS) 2001 are reported as unknown. The Event Data Recorders (EDRs), now being installed as standard equipment by several automakers, have the potential to provide an independent measurement of crash severity which avoids many of the difficulties of accident reconstruction techniques. This paper evaluates the feasibility of replacing delta-V estimates from accident reconstruction with the delta-V recorded by EDRs. The analysis is based on over 500 NASS/CDS cases from 2000 2002 which have corresponding EDR datasets. The potential of extracting manual belt use from EDRs is also discussed and compared with the corresponding results from NASS gathered by accident investigators. Although EDRs can greatly enhance the investigation of a crash, the study finds that current EDRs are not perfect. The paper discusses the limitations of current EDR technology and the opportunites for enhancement of future Event Data Recorders.

Crash performance of strong-post W-beam guardrail with missing blockouts

Missing blockouts in a strong-post w-beam guardrail, a condition most commonly associated with environmental decay or crash damage, has never been thoroughly investigated. To determine the risks posed by the removal of a blockout, a combination of component-level pendulum testing and full-scale finite element models of crash tests was used to assess whether a missing blockout renders the guardrail performance unacceptable. Finite element models were developed for three pendulum tests. (1) A 30.1-kph impact into a test installation with proper blockout installation resulting in containment, (2) a 30.5-kph impact into a test installation with one missing blockout resulting in splice rupture, and (3) a 26.7-kph impact into a test installation with one missing blockout resulting in containment. The finite element model was able to reproduce the splice failure in test 2 when the appropriate mesh quality and failure criteria were used. Full-scale crash test models of a 2000-kg pickup truck striking a 29 post guardrail at 25° were developed. The simulation results indicated that wheel snagging was not a major problem. Although a missing blockout increases the maximum rail tension and deflection by as much as 13%, such guardrails are still capable of safely redirecting of vehicles.

Limits of Acceptable Rail and Post Deflection in Crash-Damaged Strong-Post W-Beam Guardrail

The guidelines for the testing of strong-post W-beam guardrail, intended to ensure the safety of errant vehicles, are specified in NCHRP Report 350. A limitation of these tests is that they are always performed on new, undamaged guardrail, whereas guardrail along highways is in a continuous cycle of damage and repair. No tests have ever evaluated the performance of deflection-damaged guardrail. A full-scale, two-part crash test was conducted to evaluate the performance of a guardrail with 14.5 in. (368 mm) of prior crash damage. When this guardrail was struck by a 4,409-lb (2000-kg) pickup truck traveling at 62 mph (100 km/h), the vehicle vaulted and came to rest upright behind the barrier. A critical factor was the failure of a post to separate from the rails. Finite element models were used to evaluate the guardrail performance at lower levels of deflection. The crash tests and finite element models demonstrated that rail-and-post deflection of 11 in. (279 mm) or higher resulted in vaulting or rollover. Repair was recommended for strong-post W-beam guardrail with combined rail-and-post deflection exceeding 6 in. (152 mm). This limit allows a margin of safety for variations in soil strength and vehicle height. The existence of rail-only deflection had a minimal effect on the crash performance up to the maximum tested value of 6 in.