The report released Thursday says the project does not answer the city's transportation problems and does not reduce operating expenses.
The Central Subway was designed to extend Muni's Metro service from the Financial District to Chinatown. However, the report criticizes the proposed route saying it could worsen Muni's on-time performance rate.
The grand jury also predicts the new subway will add to the city's deficit and may push transit maintenance to "the breaking point."
