LOS ANGELES (CBSLA.com) — Voters overwhelming passed Measure M that will raise the countywide sales tax by a half-cent to fund transportation projects in Los Angeles County.

Over the next 40 years, M is supposed to pump $120 billion into projects that would improve and build rail lines, streets and freeways to relieve traffic congestion.

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But don’t expect to see much relief any time soon. Some experts predict commuters will not see any radical reduction, as much as 15 percent, in commuting time for another 40 years, and Metro officials agree.

“At the top of the list in terms of going into construction is the 96th Street station that will be a connection to LAX,” said Pauletta Tonilas, Chief Communications Officer at LA Metro.

That project is scheduled to break ground in 2018.

Then there’s “the Orange Line, BRT (Bus Rapid Transit), also the Gold Line Extension to Claremont,” Tonilas said.

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There’s also talk of digging a tunnel under the Sepulveda Pass to relieve the usual bumper-to-bumper traffic.

“We currently are in receipt of three unsolicited proposals from the private sector for the Sepulveda Pass,” Tonilas confirmed.

Whether or not it’s a tunnel, construction in the heavily traveled route could be four years away, she said. “Could” is the operative word here.

A Metro extension that would connect Little Tokyo and Downtown has been under construction for a while and is being funded by Measure R, which was passed eight years ago.

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The half-cent sales tax increase from Measure M kicks in on July 1 for the next four decades.