Before Portage and Burns Glaciers began their latest retreats, early traders, miners, and indigenous peoples traveled across these glaciers using them as a 'portage' between Prince William Sound and Cook Inlet. Today, the railroad and tunnel to Whittier provide this important link for people. This is a 2.5 mile one lane tunnel. It uses a computerized traffic control system that regulates both rail and highway traffic. There is an 8 lane staging area controlling how the traffic enters the tunnel.