Voters in Los Angeles County have approved a sales tax hike to raise tens of billions of dollars for an array of rail and road improvement projects, election results early Wednesday morning indicated.

With all precincts reporting, 70 percent of voters supported Measure M, more than the two-thirds threshold required.

Measure M hikes the sales tax to generate roughly $860 million a year to fund major transportation projects such as a rail tunnel under the Sepulveda Pass and rail-line extensions in the San Fernando and San Gabriel valleys. The measure extends the most recently enacted half-cent sales tax hike, Measure R, and institutes a new half-cent sales tax increase, keeping both in place permanently.

The Los Angeles Area Chamber of Commerce and most other major business groups in Los Angeles County supported the measure, saying it will create construction jobs and help ease congestion. But it faced a tough battle to get the required two-thirds majority amid opposition from several South County communities that feel projects in their region are slated for the too-distant future.

A previous attempt to pass a half-cent sales tax increase for transportation projects in 2012 received 66.1 percent of the vote, coming up just short of the required two-thirds majority. Transportation officials responded by adding more projects into this latest measure in the hopes of garnering more votes – a move that succeeded.

Public policy and energy reporter Howard Fine can be reached at [email protected]. Follow him on Twitter @howardafine.