This post is by John Norquist, CEO and president of the Congress for the New Urbanism and the former mayor of Milwaukee.

“When you're in a hole, stop digging.” Advice like that comes cheap and sometimes ignoring it can cost billions of dollars. For Boston, ignoring it cost $22 billion to be exact. If Boston had it to do over, would they spend $22 billion (the original estimate was $5.8 billion) on tunnels and capped super highways?

Many might say yes because the federal government, meaning the rest of America, paid for most of it. But even with “free” federal money, did the Big Dig add the most value to downtown Boston? Sure, the capped tunnel is better compared to the elevated Artery. But it didn’t really reduce congestion. It lengthened automobile trips and relocated congestion to other choke points. And other projects could have increased regional mobility at a cheaper price.

Building a waterfront tunnel in Seattle offers a similar value proposition, though the scales are even more tilted to a simpler option. Yes, there are 110,000 cars using the viaduct now. But the projected growth that the Washington State Department of Transportation has based its planning on is contradicted by recent data, including a comprehensive study by the Center for Neighborhood Technology that shows automobile trips in have declined by six percent from 2000 to 2009. Furthermore, highways with similar traffic volumes in New York and San Francisco have come down with good results. Besides, most of those trips are trying to get to downtown and a tunnel will mean a less direct route.

Seattle’s strong commitment to being an environmental leader should begin with reducing car trips, not increasing them, and providing transportation options that can be used by all its citizens.

Seattle taxpayers are sliding down the road to building the “Big Dig West” but without the critical federal money pot. One would think that the lack of federal funding would lead to a clearer evaluation of the costs and benefits. But with eight of the nine Seattle City Council members supporting the tunnel plan, it looks like city taxpayers will be on the line for likely cost overruns. Tunnels are notorious for cost increases. After all, you only find out what's really down there after you start digging.

Mayor McGinn already knows it is time to stop digging; hopefully the city will heed that advice before it’s too late.