California's high-speed rail project is going ahead despite false media reports last winter that Gov. Gavin Newsom had pulled the plug. But it still faces serious challenges, and some key decision points are looming.

First, let's be clear about the importance of this project. A lot hinges on it.

The initial segment—the Central Valley line—is the best way to demonstrate the power of high-speed trains on a national stage. It can be transformative far beyond California. But how it’s built matters.