[adamhearn]

The tunnel is the only way, besides helicopter to get to Whittier besides the port.

https://dot.alaska.gov/creg/whittiertunnel/faq.shtml

Why is Whittier so important to the Alaska Railroad?

From an economic and geographic standpoint, Whittier represents the Alaska Railroad's only viable freight interchange point for its barge service connecting Alaska with the lower 48 states and Canada. Seward and Anchorage are not viable port alternatives for barge interline service. Anchorage is not free of ice year-round and Seward requires traveling over a mountain pass at a 3% grade (it would take six locomotives to haul a heavy load from Seward versus two from Whittier). Whittier is a year-round, ice-free, deep-water port. It is located only 50 miles from Anchorage and has slight grades for trains and engines. For these reasons, all the Alaska Railroad's railcars, locomotives, and rail-borne freight must enter and depart via Whittier.

[KennyBlanken]

That's nice but doesn't explain why the traffic system for the tunnel's one lane of car traffic is so rudimentary and restrictive.

[sufficer]

Because there is essentially no traffic

[VintageCool]

because the tunnel was built for trains, not cars. The tunnel was built by and for the military back when the base was important; there isn't enough reason to spend the money to expand the tunnel now.