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Federal Motor Vehicle Safety Standard 226 outlines a component test methodology that consists of a linear impact test that uses a featureless head-form with a mass of 18 kg to impact a vehicle's side windows' daylight openings at various positions. The test measures the excursion of the head-form beyond the plane of the window glazing. The intention is to evaluate the ability of a vehicle's ejection mitigation system, such as the curtain airbag or other vehicle features, to manage the impactor energy and limit excursion. However, there are several factors which may cause variation in the amount of excursion measured in the test. These factors include how the vehicle is restrained for the test, the friction of the linear impactor shaft and the lateral deflection of the impactor shaft among others.

With many vehicles now achieving high marks in NCAP frontal and side impact, many countries around the world are considering or have already implemented pedestrian impact protocols to help address these types of crashes, due to the incidence rate of pedestrian injuries and fatalities. The leading global protocol put forth by the working party No. 29 (WP29) of the United Nations is the Global Technical Regulation (GTR) [1], which includes testing that simulates a pedestrian's head impacting a vehicle's hood through the use of a free flight head form. In conducting this test, it is important to be aware of the sources of variation inherent in the testing equipment and testing methodology so that steps can be taken to mitigate their influence. Testing facilities that can maintain high standards of repeatability can be relied on for producing valid tests that meet the GTR tolerances as well as maintaining reasonable costs and testing throughput.

The National Highway Traffic Safety Administration (NHTSA) has identified ejection mitigation as a top priority, issuing a final rule for FMVSS 226, Ejection Mitigation, in January of 2011 to set performance standards for a vehicle's ejection mitigation countermeasures to mitigate the risk of ejection through a vehicle's side window openings. The most likely countermeasures to be used for compliance with this standard are rollover activated curtain airbags that deploy from a vehicle's roof rail. However, this rule will most likely result in increases in the coverage area and inflator outputs of the curtain airbag; which may influence out-of-position occupant injury as measured in the test methods that have been outlined by the Side Airbag Out-of-Position Injury Technical Working Group (TWG).