Some story plots are as old and predictable as the ages. The bad witch always gets her comeuppance, Sherlock Holmes always solves the case, and municipalities always struggle to find and to fund transit solutions.

This week, Miami-Dade county officials will move forward with a plan to improve transit — they are just not sure yet whether that will go toward building 20 miles of new rail (a supplement to the 25-mile existing Metrorail system) for $1.3B, or buying modern rapid-transit buses that cost about 80% less. The Transportation Planning Organization governing board will decide with a vote Aug. 30.

As the Miami Herald reported, in 2002, Miami-Dade County voters approved a half-penny tax that was meant to improve rail and bus routes. Funds were supposed to help link major suburbs to Miami, and to improve connections between downtown Miami and Miami Beach (now served by causeways that go over the waters of Biscayne Bay).

The half-penny tax generates about $290M a year, but following the housing crisis of 2008, funds were diverted to pay for operating costs of existing transit. (Operating costs had been funded by property taxes, but those revenues dropped with property values.)

In 2016, Miami-Dade and the TPO developed the Strategic Miami Area Rapid Transit Plan to advance six transit corridors. The current battle concerns one of those corridors, South Dade, that serves bedroom communities south of Miami like Cutler Bay. With the economy now improved, some south county residents argue they should get the rail they were promised. One county commissioner is leading a legal challenge to stop the diversion of the half-penny tax.

The county mayor, Carlos Gimenez, initially supported rail but now says it is just too expensive. The Metrorail would cost $1.3B to build and $67M per year to run, according to Miami Today. The existing Metrorail already costs $76M to operate. According to a county study, rail would eat up 74 cents of every available transit dollar for the next 40 years, whereas the $243M bus system would consume just 12 cents of every dollar.

Some rail advocates have argued that federal funds could supplement the county contribution, but Gimenez has countered that is not feasible and that spending so much on rail in the south would starve other, denser parts of the county that have yet to see investments in transit improvements. Buses could also get running more quickly than rail — but then again, bus ridership has fallen steadily (a 25% drop since 2013) and if rail is ever to be built, it must begin sometime.

The 25-member board that will vote Thursday includes all 13 county commissioners plus mayors and others.