SANDAG has a new transportation plan. Now it must convince voters to pay for it.

The San Diego region has a new blueprint for what its transit network should look like by 2050 — but high costs and the will of voters could create plenty of headwinds in the future.

The Board of Directors for the San Diego Association of Governments inked a $125 billion regional plan on Friday, with elected officials commending the package as far more transparent and realistic than those from years past.

Required by law, the regional plan identifies projects SANDAG wants the region to build by 2035 and by 2050.

The document is a broad-strokes wish list for the future of transit in San Diego. Dozens of projects are included, from bike lanes along the coast and new freeway lanes in North County to safety improvements on the rural highways of the backcountry.

“This is kind of the big snapshot,” SANDAG CEO Mario Orso told the board on Friday.

Escondido Mayor Dane White was the only member of the board to vote against the plan.

With the regional plan, SANDAG must do more than identify what projects it wants to build — it must also show how it’s going to pay for them.

To finance the regional plan, SANDAG has made a key assumption: that voters will back two separate ballot measures to raise sales taxes between now and 2050.

One of them is a half-cent ballot measur...