 The highway descends to Dillon Reservoir , near the town of Frisco , and begins one final ascent to the Eisenhower Tunnel , where the freeway crosses the Continental Divide . At the time of dedication , this tunnel was the highest vehicular tunnel in the world , at 11 @,@ 158 feet ( 3 @,@ 401 m ) . As of 2010 , the facility was still the highest vehicular tunnel in the United States . The Eisenhower Tunnel is noted as both the longest mountain tunnel and highest point on the Interstate Highway System . The tunnel has a command center , staffed with 52 full @-@ time employees , to monitor traffic , remove stranded vehicles , and maintain generators to keep the tunnel 's lighting and ventilation systems running in the event of a power failure . Signals are placed at each entrance and at various points inside the tunnel to close lanes or stop traffic in an emergency . There are several active and former ski resorts in the vicinity of the tunnel , including Breckenridge Ski Resort , Keystone Resort , Arapahoe Basin , Loveland Ski Area , Berthoud Pass Ski Area and Winter Park Resort . 
