In very populated areas where the traffic volume is the greatest, the speed limit can drop as low as 55 miles per hour.

Colorado had already begun planning a modern inter-city route along the Front Range as early as 1944.

The first section of freeway was also in 1944 which would later become Interstate 70 that originally terminated near I-25 in Denver before getting extended across the Rocky Mountains along the US 6 and US 40 corridors.

It originally was proposed by CDOT to be designated as Interstate 425 but it was rejected by AASHTO and was renumbered to I-270 on February 26, 1959, about six years before construction began between I-70 and Vasquez Boulevard.

[10] A full beltway around Denver was proposed by CDOT as well and was added to the Federal Highway Act of 1968 and was to be Interstate 470.

The beltway was later extended east of I-25 and is now a toll road known as E-470 and then eventually west of I-25 north of Denver, known as Northwest Parkway.