The purpose of the reported test program was to develop modifications to existing malleable aluminum transformer bases for highway luminaires that could be performed in the field with minimal equipment and labor expenditure. The evaluation consisted of two phases; first, determining whether the modifications resulted in acceptable breakaway performance as indicated by the momentum change of the impacting vehicle, and, second, determining whether the modifications could result in a serious degradation of expected service life as indicated by results of a limited accelerated fatigue study. The dynamic tests were conducted in accordance with NCHRP Report 153 and used a 1020-kg (2250-lb) car impacting at 9 and 18 ms (20 and 40 mph). Fatigue tests consisted of vibrating a horizontally mounted base and pole shaft at the resonant frequency of the pole until failure occurred. The tests indicated that a base saw cut, made horizontally to leave 76.2 mm by 4.76 mm (3 x 3/16-in) thick metal on each side, would induce approximately 362 kg-s (800 lb's) momentum transfer and 6 g 50 millisecond maximum average deceleration in the test vehicle. Terminating the saw cut in 38-mm (1 1/2-in) diameter holes proved sufficient to induce fatigue failure in the unmodified pole instead of the base./Author/