The Devil's Slide tunnels, a pair of mile-long tunnels in Pacifica, Calif., will be opened to motorists once crews are done with final safety tests. The $439 million tunnels have huge exhaust fans, carbon monoxide sensors, fire-resistant shelters and two, 1,000-foot bridges that are 125 feet high. "A new highway tunnel is a rare beast in this country, and what they are doing at Devil's Slide is certainly different than anything we've seen in the U.S.," said Neil Gray, director of government affairs at the International Bridge, Tunnel and Turnpike Association.