8 out of the 12 counties which form the Denver-Aurora-Boulder Combined Statistical Area are serviced by an agency known as the Regional Transportation District. Organized in 1969 and beginning operations in 1972, RTD serves an area of over 2 million people as this is the 16th most populous metropolitian area in the United States.

Type: Public

Fleet Size: 240 Low Floor Buses

Routes: 138

Manufacturer and Powerplant: The bulk of RTD's bus fleet is composed of Orion and Gillig models which are being slowly retired from service to be replaced by an order of New Flyer Xcelsior XD models, some of which entered service in 2014. RTD's Light Rail services are carried out by older Siemens rail cars.

Fare Collection: There is currently only a limited Contactless Card Payment System in Denver-Aurora sold to employers to give to employees and colleges to give to students. A card for the general public is being developed by Xerox expected to be released soon. RTD's current fare structure is extremely archaic in that it still uses zone pricing a practice which fell out of favor in the early 90's.

Livery: RTD livery typically consists of a white backdrop hosting themes of Blue with Red, Orange and Yellow striping. RTD does sell the sides of its fleet for advertising space.

Innovations: Notably unique to RTD, buses in its fleet are fitted with special "Yield" turn signals which alerts drivers to give way to turning buses as per Colorado Law under which, yielding to buses is required.