Between an upcoming wave of retirements at the T and an increasingly difficult labor market, the Massachusetts Taxpayers Foundation — the think tank behind the report — forecasts an uphill battle.

“A sufficient workforce is the most fundamental ingredient necessary for a transit service that’s safe, reliable, and serves our economy,” MTF President Doug Howgate said in a statement accompanying the report, released Monday.

“The current gap between reality and the levels of service riders and our region deserve is startling and failing to close that gap quickly will result in a cascading series of issues that raise important questions about its capabilities going forward,” Howgate continued.