Maps show the areas in dark-gray where property tax increment will be used to pay for the 5.6-mile Red Line Extension, shown on the dotted red line. [CTA/SB Friedman Advisors]

Chicago and CTA planning officials leapt forward last week in their long-promised mission to extend the city’s most used transit line by releasing a detailed funding plan that relies in part on culling future tax revenues from some downtown and Near South Side residents.

The controversial new financing mechanism promises to raise up to $950 million for the herculean rail project — not by hiking or imposing any new taxes, but by diverting natural property tax growth from chunks of the Loop, South Loop, Armour Square, Bridgeport, Chinatown and Douglas neighborhoods into a special construction fund for the next 35 years.