Eisenhower-Johnson Tunnel

The Eisenhower-Johnson Memorial Tunnel carries I-70 under the Continental Divide about 60 miles west of Denver. Its west portal sits at 11,158 ft, the highest point on the entire U.S. Interstate Highway System (Wikipedia; Denver Gazette, July 2025). It is two separate bores, not one. The Eisenhower bore runs westbound at 1.693 miles. The Johnson bore runs eastbound at 1.697 miles, each roughly 1.7 miles long (CDOT; Wikipedia). It is also the longest mountain tunnel on the Interstate system, run 24/7 by CDOT with more than 30 full-time staff.

The grade inside the tunnel is mild, averaging just 1.64% rising toward the west. The trouble is the approaches. I-70 climbs about 7% on the west side and 6% on the east side, long pulls and long descents at altitude (CDOT). The tunnel itself shaves about 9.1 miles off the old crossing over US 6 / Loveland Pass, the original way over the divide (CDOT). As of 2007 it carried about 32,260 vehicles a day. More than 434 million had passed through cumulatively by March 2023 (CDOT; Wikipedia).

For drivers of tall rigs and hazmat loads, the tunnel comes with two hard rules. Clearance is posted at 13 ft 11 in, raised from the old 13 ft 6 in by a 2007 retrofit with lower-profile lighting and signs (Wikipedia; CCJ; CDOT). Placarded hazardous-materials loads are banned year-round, sent instead over Loveland Pass. Both rules shape how trucks plan this stretch of I-70.

• West portal sits at 11,158 ft (3,401 m), the highest point on the U.S. Interstate system (Wikipedia; Denver Gazette, 2025).
• Two two-lane bores: Eisenhower (westbound) at 1.693 miles, Johnson (eastbound) at 1.697 miles (CDOT; Wikipedia).
• Posted clearance is 13 ft 11 in (4.24 m) after a 2007 retrofit raised it from 13 ft 6 in (Wikipedia; CCJ; CDOT).
• Tunnel grade averages 1.64%, but the I-70 approaches run about 7% west and 6% east (CDOT).
• Placarded hazmat is banned year-round; about 200 hazmat trucks a day take Loveland Pass instead (Summit Daily; Wikipedia).
• Saves about 9.1 miles versus the old US 6 / Loveland Pass route (CDOT).
• Carried about 32,260 vehicles per day as of 2007; over 434 million cumulatively through March 2023 (CDOT; Wikipedia).

Colorado's traction and chain laws cover I-70 through the tunnel and can be in effect Sept 1 through May 31, from Dotsero (MP 133) to Morrison (MP 259), which includes the tunnel (Colorado State Patrol; CDOT). Under the Passenger Vehicle Traction Law, vehicles under 16,001 lb need snow tires, M+S-rated tires, or chains/AutoSock, all with at least 3/16-inch tread. When the Commercial Vehicle Chain Law is active, commercial vehicles over 26,001 lb must chain up, with the standard requirement being chains on a minimum of four drive tires (TA Trans summary of CDOT rule). CDOT directs trucks to designated chain stations along the mountain corridor. The official page reviewed does not name hard staging points on this stretch.

There is no fixed closure schedule. The tunnel closes or runs reduced operations for crashes, fires, over-height alarms, avalanche-control work on the approaches, and severe winter weather. During peak demand CDOT uses metering instead of full closure. Traffic is held outside the portals when volume tops the corridor's capacity, with stops averaging about 20 minutes, because the bores have only two lanes and no shoulders for emergency response (CDOT metering page). An over-height vehicle triggers an automatic closure. A siren sounds, signals turn red, and the entrance stays shut until the vehicle is cleared (Wikipedia). When Loveland Pass closes, which it usually does before the tunnel in severe weather because it is higher and exposed, CDOT escorts waiting placarded-hazmat loads through the tunnel in convoys, typically at the top of each hour, holding other traffic for about 15 minutes (CDOT metering page; Summit Daily).

During construction the project was called the Straight Creek Tunnel, after the creek along the western approach. It was renamed before dedication to honor President Dwight D. Eisenhower and Edwin C. Johnson, the Colorado governor and U.S. senator who pushed for an Interstate across the state (Wikipedia; Westword). The first bore, the westbound Eisenhower, opened in 1973. The eastbound Johnson bore followed in 1979. CDOT dates the Eisenhower work from March 15, 1968 to March 8, 1973, and the Johnson work from Aug 18, 1975 to Dec 21, 1979 (CDOT; Wikipedia).

It came hard. The Eisenhower bore was estimated at $42 million but cost about $108 million, roughly $783 million in 2025 dollars. Fault zones missed in the pilot bore bankrupted the first contractor and forced emergency measures against cave-ins (Wikipedia). The construction killed seven workers, three on the Eisenhower bore and four on the Johnson bore (Wikipedia). In 2016 CDOT switched on a $25 million fixed water-deluge fire-suppression system, about 18,000 ft of insulated, heat-traced pipe carrying roughly 30,000 gallons, designed to cool rather than extinguish a fire so firefighters can get close (Aspen Times / CBS Colorado; Summit Daily; CDOT).