All five expressways are all electronic toll roads, requiring the use of SunPass or a "toll-by-plate" program and do not accept cash, and the free movement sections were removed. The Gratigny Parkway, Don Shula Expressway, and Snapper Creek Expressway became all electronic in 2010, while the Airport Expressway and Dolphin Expressway were converted 2014. Completely funded by toll revenues, MDX has been aggressively upgrading and updating its roads over the past decade, including the ongoing Dolphin Expressway extension and re-engineering of several interchanges of its two oldest expressways. Long-term plans include the redesign and reconstruction of longtime bottlenecks in the Shula and Dolphin Expressways, most notably the often-backed-up Killian Parkway/SR 990 interchange near Miami Dade College-Kendall Campus and the heavily congested interchange with the Palmetto Expressway near the extreme southwestern end of Miami International Airport.
Markings
All MDX highways use the shield-shaped signs reserved by FDOT for toll roads, with the MDX logo attached below the "shield". In addition, all MDX highways use a uniquely designed mileage marker. Instead of the green "MILE XX" markers commonly seen on interstate highways, the five MDX expressways use blue mileage markers featuring : a single letter indicating the direction of travel, the State Road designation of the highway, and two numbers separated by a horizontal line. These markers are placed on the edge of the shoulder every 0.2 miles along the expressway. The Gratigny Parkway has two of these. Prior to the removal of free movement sections, on portions of a MDX route where no tolls are ahead, the TOLL in the green section of the TOLL shield was removed.
Airport Expressway
State Road 112, locally known as Airport Expressway is a 4-mile-long east–west expressway connecting Miami International Airport in Miami to I‑95 and I-195, which ultimately connects to Miami Beach.
Dolphin Expressway
State Road 836, locally known as the Dolphin Expressway, is a 13.8-mile-long toll road currently extending from Southwest 137th Avenue in the west to I-95 in the east. The section of roadway east of I-95 is designated as I-395 or the MacArthur Causeway.
State Road 878, locally known as the Snapper Creek Expressway, stretches for 3 miles between Don Shula Expressway and U.S. Highway 1. This provides access to Kendall and South Miami. Although constructed, improved and maintained through toll revenue, the Snapper Creek Expressway was untolled until July 17, 2010, when open road tolling was initiated on the Expressway.
Gratigny Parkway
State Road 924, locally known as Gratigny Parkway, is a 5.2-mile-long limited access all-electronic toll road maintained by the Miami-Dade Expressway, running east to west. The Gratigny Parkway starts east of the Palmetto Expressway/I-75 interchange in Hialeah and ends at Northwest 32nd Avenue in North Miami. The section of roadway east of NW 32nd Avenue is a surface street also known as Gratigny Road. Despite its relatively short length, SR 924 is a major east–west artery in northern Miami-Dade County, Florida.
