Page:Highway Needs of the National Defense.pdf/61

Rh capacity by the standard adopted. The deficiency is slight in respect to 2,207 bridges, 1,444 on rural sections of the system and 763 on urban sections, which are rated as of H20 design. All other existing bridges are of definitely inferior strength for the interstate system. The numbers thus deficient are 7,218 in rural areas and 1,016 on urban sections of the system.



Deficiency of bridge clearance

But it is not alone in carrying capacity that the existing bridges are deficient. ‘They are more seriously deficient in horizontal clearance and to some degree in the vertical clearance they provide.

None of the H20-S16 bridges, in either rural or urban areas, is deficient in vertical clearance. However, there are 905 of the bridges of this standard capacity in rural areas that are in some degree inadequate in horizontal clearance. Of these, 627 are substantially inadequate; the remainder are only moderately inadequate.