Stopping sight distance (SSD) is the minimum sight distance required and shall be provided continuously. Decision sight distance (DSD) is desirable at interchanges, intersections, lane drops, and areas of complex decision-making. Intersection sight distance (ISD) shall be provided at all at-grade intersections. Passing sight distance applies to two-lane highways and determines no-passing zone marking. CDOT uses the AASHTO criteria with a perception-reaction time of 2.5 seconds and deceleration rate of 11.2 ft/s².
References: AASHTO current edition, CO Standard Specifications, FHWA Technical Advisories, and applicable federal regulations (23 CFR). Contractors shall maintain current copies of all referenced standards on the project site.
Source: CDOT Highway Design Manual, 2024 Edition. Pages 11–12 of 37.