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of the 785 crossings of sidings and spur tracks can be determined only by a careful analysis in each case, giving proper weight to traffic hazard and delay and inconvenience.

Of the 760 grade crossings that definitely should be eliminated, 574 are on urban sections of the system. Only 186 are on rural sections. When these figures are compared with the 1,051 urban and 1,013 rural crossings that already have been separated by the construction of underpass or overpass structures, it is apparent that the work of grade-crossing elimination to date has been much more thorough on the rural than on the urban sections of the system.

Elimination of main-line railroad grade crossings in urban areas often requires extensive construction, as is evident in this sketch of a proposed treatment on U S Route 40 in Ohio.

DEFICIENCY OF INTERSECTIONS WITH OTHER HIGHWAYS

There are 118 intersections of rural routes of the designated system with other highways at which the combined hourly traffic on the inter-