Horizontal alignment design shall follow AASHTO Green Book criteria for design speed, radius, superelevation, and sight distance. Minimum curve radius is determined by the design speed and maximum superelevation rate. ODOT uses a maximum superelevation rate of 6% for rural highways and 6% for urban facilities. Compound curves require a ratio of long radius to short radius not exceeding 1.5:1. Broken-back curves (closely spaced curves in the same direction) are discouraged per OR design policy.
All work under this section shall comply with ODOT current standards and applicable AASHTO, ASTM, and federal requirements. The Engineer has authority to accept or reject materials and workmanship that do not conform to the specifications.
Source: ODOT Highway Design Manual, 2024 Edition. Pages 5–6 of 37.