The probabilistic evaluation of aluminum decks in flexure between girders, using AASHTO LRFD specification is presented. The results show that the evaluated deck is in conformity with AASHTO LRFD specification as regards the target safety value for bridges of 3.5 for load resistance of 1.0, since its safety value is higher than the code prescription that is 4.44 for LRF of 1.0 and 3.39 for LRF of 1.1. These results indicate that aluminum decks as suggested by AlumadeckTM met the requirement for bridge decks and have the ability to carry more live loads than conventional reinforced concrete decks. Also, a comparative study of safety margins of composite action between aluminium decks on steel girders and concrete decks on steel girders gave results that show that AlumadeckTM as proposed is more superior from the view point of strength and serviceability. This result of AlumadeckTM to conventional concrete decks gave a safety index value of 17.33 for the full composite action while that of concrete is only 11.83.