Interchange types include diamond, parclo, single-point urban (SPUI), and system interchanges. NCDOT requires an Interchange Justification Report (IJR) or Interchange Modification Report (IMR) per FHWA policy for all new or modified interchanges on the Interstate system. Minimum ramp design speed is typically 70% of the mainline design speed. Acceleration and deceleration lane lengths per AASHTO Green Book Table 10-3 and 10-4.
All work under this section shall comply with NCDOT 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: NCDOT Highway Design Manual, 2024 Edition. Pages 19–20 of 37.