From the beginning, the Metrorail was designed and envisioned to have more lines than the current two line system; however, the federally subsidized cost of the original line ended up over budget at $1.02 billion, after which ridership was much lower than expected.
The proposed lines included:
The 13.6 mi (21.9 km) Biscayne/Northeast Corridor following U.S. Route 1 (Biscayne Boulevard) from Government Center up to the Broward/Miami-Dade county line in Aventura.

The 9.5 mi (15.3 km) North Corridor up NW 27 Avenue to the county line.

The 17.2 mi (27.7 km) East–West Corridor from Government Center west to the Florida International University main campus in University Park, as well as east from Government Center to the Port of Miami.

The 5.1 mi (8.2 km) BayLink from Historic Overtown/Lyric Theater station to South Beach, Miami Beach.

The South Link, a 21 mi (34 km) extension of the Green Line from Dadeland South to Florida City.

The 4.5 mi (7.2 km) Douglas Road extension from Douglas Road station to the Miami Intermodal Center.

The 15 mi (24 km) (West) Kendall Corridor down Kendall Drive from Dadeland North station west to West Kendall and north to the FIU main campus.

It was not until the half-penny transit tax was passed in 2002 that any serious expansion plans were again considered, with the North Corridor and East–West lines, both dubbed the "Orange Line," assuming the highest priority, while the possibility of 88.9 miles (143.1 km) of additional rail if all the extensions were built by 2030, was touted.
However, after budget deficits, other uses of the tax revenue, and a downgrade of the North Corridor's funding priority to medium-low by the federal government, after 10 years only the 2.4 mile AirportLink and Orange Line remained promised and realized.

The credibility of Miami-Dade Transit and the County as a whole, including the validity of their ridership estimates and revenue forecasts, has been a significant impediment to their qualifications for funding under the Federal Transit Administration's (FTA) approval.
In 2011, Miami-Dade Transit underwent a serious federal investigation and takeover by the FTA in which it was forced to open its books over suspicions of money mismanagement.
The Agency threatened to cease its funding used to cover operational costs, which would have meant significant cuts in service; however, they took the funding under their strict control to prevent this from happening.

The South Link expansion, which was intended to replace the South Miami-Dade Busway, a bus rapid transit that opened in segments on February 3, 1997 and in April 2005, has plans for a widened right of way, elevated crossings at major intersections, as well as the possibility of building one additional Metrorail station at SW 104 Street to alleviate traffic and parking in Dadeland.
On 2009, the Metropolitan Planning Organization has proposed that the busway be opened to regular vehicle traffic by adding a SunPass toll system with the profits going towards busway improvements.
From the beginning, the Metrorail was designed and envisioned to have more lines than the current two line system; however, the federally subsidized cost of the original line ended up over budget at $1.02 billion, after which ridership was much lower than expected. The proposed lines included:
The 13.6 mi (21.9 km) Biscayne/Northeast Corridor following U.S. Route 1 (Biscayne Boulevard) from Government Center up to the Broward/Miami-Dade county line in Aventura.
The 9.5 mi (15.3 km) North Corridor up NW 27 Avenue to the county line.
The 17.2 mi (27.7 km) East–West Corridor from Government Center west to the Florida International University main campus in University Park, as well as east from Government Center to the Port of Miami.
The 5.1 mi (8.2 km) BayLink from Historic Overtown/Lyric Theater station to South Beach, Miami Beach.
The South Link, a 21 mi (34 km) extension of the Green Line from Dadeland South to Florida City.
The 4.5 mi (7.2 km) Douglas Road extension from Douglas Road station to the Miami Intermodal Center.
The 15 mi (24 km) (West) Kendall Corridor down Kendall Drive from Dadeland North station west to West Kendall and north to the FIU main campus.
It was not until the half-penny transit tax was passed in 2002 that any serious expansion plans were again considered, with the North Corridor and East–West lines, both dubbed the "Orange Line," assuming the highest priority, while the possibility of 88.9 miles (143.1 km) of additional rail if all the extensions were built by 2030, was touted. However, after budget deficits, other uses of the tax revenue, and a downgrade of the North Corridor's funding priority to medium-low by the federal government, after 10 years only the 2.4 mile AirportLink and Orange Line remained promised and realized.
The credibility of Miami-Dade Transit and the County as a whole, including the validity of their ridership estimates and revenue forecasts, has been a significant impediment to their qualifications for funding under the Federal Transit Administration's (FTA) approval. In 2011, Miami-Dade Transit underwent a serious federal investigation and takeover by the FTA in which it was forced to open its books over suspicions of money mismanagement. The Agency threatened to cease its funding used to cover operational costs, which would have meant significant cuts in service; however, they took the funding under their strict control to prevent this from happening.
The South Link expansion, which was intended to replace the South Miami-Dade Busway, a bus rapid transit that opened in segments on February 3, 1997 and in April 2005, has plans for a widened right of way, elevated crossings at major intersections, as well as the possibility of building one additional Metrorail station at SW 104 Street to alleviate traffic and parking in Dadeland. On 2009, the Metropolitan Planning Organization has proposed that the busway be opened to regular vehicle traffic by adding a SunPass toll system with the profits going towards busway improvements.
Metrorail (Miami-Dade County)