This paper presents two methods for determining the lateral deflection and the basic movement of a plastic waterfilled
barrier (PWB) system after an impact. In the first method theoretical equations are developed based on the
conservation of energy while MADYMO simulations are used in the second method of estimating lateral deflections. Crash
tests on various PWB systems carried out by different institutions including Monash University are used to validate the
results from both the theoretical calculations and the MADYMO models.