Gov. Sean Parnell wants to spend $2 million more on prep work for a 500-mile road to Nome that has a megaproject price tag and no guarantee that it will open up workable mining prospects in northern Alaska.

Dowl HKM did a $1 million study that recommended a route from Manley Hot Springs, about 160 miles west of Fairbanks, that would cost from $2.3 billion to $2.7 billion -- or $4.6 million to $5.4 million per mile. The route would follow the Yukon River for much of the way, connecting villages like Tanana, Ruby, Galena, Nulato and Koyuk with the state's road system.

Exciting? No question. Imagine driving from Anchorage to the Bering Sea. Imagine a Yukon highway.

Some lawmakers gasp at the price tag. They should. Others argue that Alaska hasn't had a big, daring project in decades and that we're overdue. That's an understandable feeling but not a rational basis for building a massive project. Besides, we have a massive project we're pushing -- the gas line.

State Rep. Woody Salmon, who represents much of the affected area and leans in favor of the road, points out that even if the price is right the road will come with its own set of woes -- land squabbles and what he called the problems that come with an influx of people.

Here are several issues lawmakers and all of us should think about.

• What resources would it open up? Parnell's notion is to build the road in stages, from one "resource deposit" to the next. The implication is that each stage will open mining or other paying opportunities, justifying the road's expense. But that's not clear from the Dowl report, which noted that while gold, silver and other mineral potential exists, there's been little exploration to prove it.

Other state-funded road projects have been to proven deposits -- lead and zinc at the Red Dog mine, gold at Pogo. Those weren't speculative roads. They were state investments in projects that promised returns on investment in jobs, taxes and business for Alaska vendors.

If the Yukon corridor is so resource-rich, then let some mining outfits share the costs of that $2 million in further study.

• What opportunities? One argument for the road is that it will open opportunities and cut fuel costs in villages on the route. That's a compelling argument if true. One of the toughest challenges for Bush Alaska is to figure out how to make a sustainable mix of subsistence and cash economies work, how to create more opportunities off the beaten path. One answer is to take the beaten path to villages.

But lawmakers should get a clear-eyed analysis on just how much costs would come down with a road. And just how much more opportunity it would bring. Any unintended consequences?

Intuitively, the opportunity argument works. But Alaska needs more than intuition before we send out survey crews and build construction camps.

• Who pays? Uncle Sam? Maybe, but that's speculative too -- hear those echoes of "Bridge to Nowhere?" Would we tap our current surplus for such a project? Sell bonds? How will we cover the estimated $40 million in maintenance costs? Keep the fuel tax? And what else is competing for all that money?

Alaska hasn't built its last major road. A road to Nome could be the next. But it's a long way from shovel-ready. At $2.7 billion, we need more reason to build than "because it's not there."