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Concrete bridge approach slabs (BAS) are used at the interface between bridge abutments and pavements that rest on compacted embankment. The objective of this research was to develop optimal cost BAS designs for new and replacement slabs. Two solutions presented here include a cast in place (CIP) design for new construction and novel precast prestressed slab (PCPS) designs for new construction and replacement of BASs. Practices of different US state Departments of Transportation (DOT) for BASs were evaluated and compared to the current practices of Missouri DOT (MoDOT). Based on the practices, a twenty feet span was chosen and finite element models were analyzed considering different slab lengths, thicknesses, and loss of support conditions to calculate maximum moments, deflections, and end slopes. Based on predicted values, CIP and PCPS design alternatives were recommended. Recommended alternatives are estimated to have a lower cost, and an equal or better performance compared to the current MoDOT designs. Currently a new study has been initiated where the recommended BAS designs are being implemented in the field