25 CFR 170.455 - How are design standards used in IRR projects?
The standards in this section must be applied to each construction project consistent with a minimum 20-year design life for highway projects and 75-year design life for highway bridges. The design of IRR projects must take into consideration:
(a) The existing and planned future use of the IRR transportation facility in a manner that is conducive to safety, durability, and economy of maintenance;
(b) The particular needs of each locality, and the environmental, scenic, historic, aesthetic, community, and other cultural values and mobility needs in a cost-effective manner; and
(c) Access and accommodation for other modes of transportation.