Ethiopia is one of the mountainous countries in Africa. This topographic condition such as rough terrain,rndeep gorges of the country; river crossings and other factors aggravate the difficultness of constructionrnof roads in the country without constructing crossways which include culvert and bridges. Thus, Bridgesrnare vital structures required during roads construction.rnThe type of structure in design standard is selected on the basis of openings span in which culvertsrnspan 1 to 6m, slab bridge span 6 to 15, and up to 18m with provision, while T-Girder bridge span 10 torn20m, where sometimes span up to 24m.rnThe site visit during this study also reveals that slab bridges up to 12m and T-Girder bridges as low asrn9m span have been recorded. This lead to the requirement of the standard to narrow the span gap atrnthe boundary for selecting slab or T-Girder in the range of 10 to 15m spans.rnIn line with this the thesis of this study focused on developing computer program for analysis and designrnof slab and T-Girder bridges, in due cause solving the design problem of economical spans for slab andrnT-Girder bridges.rnA comparative study on the basis of cost of materials is conducted to select and identify the economicalrnspan range of slab and T-Girder bridges. The developed program is illustrated using particular examplernof both slab and T-Girder bridges.rnThe study has come with solution based on the prevailing rates of construction cost to be adopted forrndesign Engineerâ€™s use.