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9 data. A list of new data elements for EDR was proposed. As mation of semi-rigid barriers is estimated from a series of mentioned previously, the EDR technology is very exciting computer simulations that correlate impact severity to maxi- and promising. However, until such time that these new EDR mum barrier deflection. The impact severity (IS), calculated data elements become available, in-depth crash investigation using the following equation, has been shown to be a good will remain the primary means of obtaining such detailed indicator of the degree of loading and maximum deflection of crash data. a barrier during an impact. IS = 1 M ( V sin ) 2.4 Reconstruction of 2 Ran-off-Road Crashes where: There are a number of existing procedures that have been IS = Impact Severity developed for reconstructing special types of ran-off-road, M = Vehicle mass fixed-object crashes (14, 15, 25), including: V = Vehicle velocity = Impact angle Semi-rigid and flexible barrier Rigid barrier The IS value, in conjunction with the impact angle, can then Pole support structure yield a direct estimate of impact speed. The impact speed cal- culated from barrier deflection should be verified by energy These reconstruction procedures are based on the general loss calculations to make sure that the estimates using both principle of identifying the energy loss parameters during the approaches are consistent. collision and summing the total to determine the change in Another procedure was developed for reconstructing rigid velocity from point of impact to point of final rest. The com- barrier impacts under the study to assess rollovers on concrete ponents of the energy loss in a typical crash include: barriers (15). For impacts involving concrete barriers, there is typically no deformation/damage to the barrier. However, it Vehicle crush was found that vehicle/barrier friction was a major source of Deformation/damage of roadside feature energy dissipation during a crash. Thus, energy loss due to Vehicle trajectory deformation/damage to the barrier is replaced by vehicle/ barrier friction, which is estimated as a function of the length Energy due to vehicle crush can be estimated manually using of barrier contact. Total energy loss is then calculated as the equations from Campbell (26) or using a computerized recon- sum of energy losses due to vehicle crush, vehicle/barrier fric- struction procedure, such as CRASH3. Energy loss due to post- tion, post-impact vehicle trajectory, and the impact speed impact vehicle trajectory is estimated using equations of calculated accordingly. motion. Adjustments are made to account for skidding and As a means of verification, the vehicle crush energy is sliding. For rotating vehicles, the distance traveled is based on matched to the energy associated with the lateral velocity of the angle of rotation and the radius and the energy loss calcu- the impacting vehicle. If both energy estimates are compara- lated accordingly. Energy loss due to vehicle trajectory can also ble, the procedure is believed to be reasonably accurate. If not, be estimated using a computerized reconstruction procedure, the vehicle crush energy would be adjusted appropriately and such as CRASH3. These two energy loss items can be stan- a new estimate of the impact speed generated. This iterative dardized and incorporated into a single reconstruction proce- procedure was found to give reasonably good estimates of dure. Unfortunately, energy loss due to deformation/damage impact speed when used to evaluate findings from full-scale of the roadside feature varies greatly among the roadside fea- crash tests. tures and impact configurations, e.g., barrier length-of-need Another computerized reconstruction procedure was devel- versus barrier end impact. Thus, there is not a single proce- oped for ran-off-road crashes involving pole support struc- dure that can be used to reconstruct all ran-off-road crashes. tures, including breakaway and non-breakaway utility poles, Instead, different reconstruction procedures are needed to luminaire supports, and sign supports (25). Energy losses due accommodate the wide variety of roadside features. to vehicle crush and post-impact vehicle trajectory are esti- A reconstruction procedure for semi-rigid and flexible bar- mated using the CRASH3 program. Energy loss associated with riers was developed for the LBSS data (14). The procedure breaking or fracture of the pole is estimated based on empir- utilizes similar techniques for estimating vehicle crush and ical test data. Impact speed is then calculated from the total trajectory energy losses. Energy loss associated with the defor- energy loss.