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57 In addition, the following supplemental evaluation factors tee A2A04 Roadside Safety Features, Mr. Richard Powers of and terminology, as presented in the July 25, 1997, FHWA the FHWA issued "Draft Guidelines for Analysis of Passenger memo entitled, "Action: Identifying Acceptable Highway Compartment Intrusion." These guidelines provided recom- Safety Features," are also used for visual assessment of test mended procedures for evaluating occupant compartment results: intrusion to promote uniformity among testing agencies and the development of uniform acceptance criteria. Three levels of Passenger Compartment Intrusion evaluation were established: acceptable if intrusion does not 1. Windshield Intrusion exceed 100 mm; marginal if intrusion is more than 100 mm, a. No windshield contact but less than 150 mm; and unacceptable if intrusion is signifi- b. Windshield contact, no damage cantly greater than 150 mm and at a location where serious c. Windshield contact, no intrusion injuries are deemed likely to result. d. Device embedded in windshield, no significant intrusion e. Complete intrusion into passenger compartment Test Article Construction f. Partial intrusion into passenger compartment In November 2000, TTI performed a full-scale crash test 2. Body Panel Intrusion on the Texas T501 longitudinal barrier (i.e., safety shape) a. Yes with a soundwall.(24) The Texas T501 test installation re- b. No mained intact at the time this project was initiated. It was Loss of Vehicle Control modified and used as a structural support for the test instal- 1. Physical loss of control lations presented herein. The fascia construction methodol- 2. Loss of windshield visibility ogy used for this study was previously developed in a Cal- 3. Perceived threat to other vehicles trans research project.(19) The use of removable, relatively 4. Debris on pavement thin fascia panels attached to a support structure was used to Physical Threat to Workers or Other Vehicles minimize cost and construction time and to permit test instal- 1. Harmful debris that could injure workers or others in lations to be re-erected if additional testing on a particular rail the area face configuration was found necessary at a later date in the 2. Harmful debris that could injure occupants in other research project. The fascia panels were constructed to emu- vehicles late the geometric form of a standard concrete safety shape Vehicle and Device Condition barrier (i.e., SBC05b & ROM01).(25) 1. Vehicle Damage a. None b. Minor scrapes, scratches or dents SELECTION CONSIDERATIONS FOR CRASH c. Significant cosmetic dents TEST CONFIGURATIONS d. Major dents to grill and body panels e. Major structural damage Preliminary guidelines developed through simulation in- 2. Windshield Damage cluded three different curves for asperity angles of 45, 90, and a. None 30 degrees. In these preliminary guidelines, thresholds for sur- b. Minor chip or crack rogate measures of OCD were used to identify regions of "un- c. Broken, no interference with visibility acceptable" and "marginal/unknown" barrier performance for d. Broken and shattered, visibility restricted but each of the asperity angles. The objective of the crash-testing remained intact phase was to reduce the region of "marginal/unknown" impact e. Shattered, remained intact but partially dislodged performance as much as possible. The asperity configurations f. Large portion removed subjected to crash testing were selected to bisect regions of un- g. Completely removed known performance or to confirm points on the failure enve- 3. Device Damage lope. The results of the crash tests were used to adjust the pre- a. None viously defined passing and failing thresholds for the surrogate b. Superficial OCD measure. Using the new thresholds, the "acceptable" and c. Substantial, but can be straightened "unacceptable" regions of the guidelines for the surface treat- d. Substantial, replacement parts needed for repair ment of safety shape barriers were adjusted. e. Cannot be repaired During the crash-testing phase, emphasis was placed on asperities with 45-degree angles of inclination. Of the seven One difficulty in evaluating OCD (e.g., floorpan/toepan crash tests performed, six were performed with 45-degree damage) in tests is that the criteria are somewhat subjective and asperities and one was performed with 90-degree asperities. can be interpreted in different ways by different crash test agen- The 45-degree asperity is between the other angles investi- cies. In August 1999, at the summer meeting of TRB Commit- gated and was considered to be the most practical in terms of

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58 construction. As was discussed in the previous chapter, shal- The asperity depth for the Test 1 configuration was in- lower asperity angles allowed for greater asperity depths, tended to bisect the "unknown/marginal" region on the pre- whereas steeper angles significantly reduced the acceptable liminary guidelines (see Figure 66). It was also selected on the asperity depths. The 90-degree asperity angle yielded "un- basis of having the maximum asperity width included in the acceptable" results for almost all practical asperity depths. preliminary design guideline. This first test was to serve two The test matrix was designed to be flexible in the sense that purposes: (1) establish a data midpoint in an area that had the outcome of one test determined the asperity configuration "unknown/marginal" performance and (2) either confirm or evaluated in a subsequent test. In other words, the test matrix deny the ability to use a criterion similar to one approved was adjusted as crash tests were performed and results were for use on the single-slope barrier in the FHWA acceptance analyzed in order to maximize the information available for letter B-110. The internal energy thresholds used for pass/ adjusting and finalizing the preliminary relationships. fail criteria were to be adjusted up or down as appropriate The preliminary guidelines developed for the 45-degree based on the outcome of this test, effectively reducing the asperities (see Figure 66) were used to select two initial asper- "marginal/unknown" region of performance at that asperity ity configurations for crash testing. The asperity geometry for width in half. these tests were: If this asperity configuration passed the test, all configu- rations of lesser depth and greater width would become part Test 1: d = 25 mm, W = 559 mm, Ws = 25 mm, = 45 degrees of the newly defined "acceptable" region, and the "pass" (pickup truck impact) threshold for the surrogate OCD measure would be increased Test 2: d = 13 mm, W = 178 mm, Ws = 25 mm, = 45 degrees accordingly. If the asperity configuration failed to meet crash (pickup truck impact) test requirements, any asperity of greater depth and lesser width would also fail. In this case, some of the previously where (with reference to Figure 66): d = asperity depth, defined "marginal/unknown" region becomes part of the W = asperity width, and Ws = the spacing between adjacent "unacceptable" region, and the "failure" threshold for the asperities. surrogate OCD measure would be appropriately decreased. Figure 66. Depth versus width guideline for 90-, 45-, and 30-degree asperity angles (reproduced from Chapter 5).