The design of the structure proper, the setting up of the critical path, and the carrying through of the design project are functions of the Bridge and Structural Design Division. This Section of this Part of the Manual, however, will deal with that portion of design criteria that the street designer considers jointly or independently with other agencies.
It has been established that most often it is not economically feasible to realign or alter the grade of the rails. Therefore, consideration is mainly devoted to realignment and grade change of the highway. However, this does not mean that the possibility of a change in the railway should be overlooked.
To make this highway alignment and grade determination, it is customary for all agencies involved to make a joint field trip to the proposed site. Contour maps and aerial photographs are an invaluable aid in making an overall preliminary study. Some of the items to be noted at the proposed site are the terrain, the extent of existing improvements, and the availability of right of way. These factors will influence the decision as to the final highway alignment, whether it is more economical in terms of construction and right of way costs to build the highway over or under the rails, and possible locations for the railway shoofly and temporary highway detour. (A railway shoofly is temporary track laid on the ground or on cribwork at one side of the railroad line to allow trains to pass during the completion of a construction project.)
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