Eisenhower-Johnson Tunnel

The Eisenhower-Johnson Memorial Tunnel takes I-70 under the Continental Divide about 60 miles west of Denver. Its west portal, at 11,158 ft, is the highest point on the Interstate system. Placarded hazmat may not use it while Loveland Pass is open, and clearance is 13 ft 11 in.

The tunnel is two separate bores. Westbound traffic uses the Eisenhower bore, 1.693 miles long, and eastbound traffic uses the Johnson bore, 1.697 miles long. Each bore has two 13-foot lanes and no shoulders or pull-outs. Inside, the road climbs 1.64 percent toward the west, so the east portal sits lower, at 11,013 ft. The grades outside are steeper: CDOT puts the west approach at 7 percent and the east approach at 6 percent (CDOT).

The ceiling over the lanes is 16 ft 4 in, but message boards hang from it, so the posted clearance in both bores is 13 ft 11 in (CDOT; 2 CCR 601-8). A taller load has to cross the divide on US 6 over Loveland Pass. Placarded hazardous materials go that way too whenever the pass is open, and a few hazmat classes are barred from the tunnel even when it is closed.

CDOT staffs the tunnel around the clock with more than 30 full-time employees, all trained as firefighters, and keeps its own fire truck and tow truck on site (CDOT). In 2025 the two bores carried 12.57 million vehicles, about 34,400 a day. July averaged just over 40,000 a day (CDOT traffic counts).

• West portal 11,158 ft, east portal 11,013 ft. CDOT gives the average as 11,112 ft, and FHWA lists the tunnel as the highest point on the Interstate Highway System (CDOT; FHWA).
• Eisenhower bore (westbound): 1.693 miles, opened March 8, 1973. Johnson bore (eastbound): 1.697 miles, opened December 21, 1979 (CDOT).
• Posted clearance is 13 ft 11 in in both bores (2 CCR 601-8; CDOT).
• Grade inside the tunnel is 1.64 percent rising to the west. The approaches are 7 percent on the west side and 6 percent on the east side (CDOT).
• Placarded hazmat must use US 6 over Loveland Pass whenever the pass is open (2 CCR 601-8, Rule 3.02).
• The tunnel is at I-70 milepost 213. Commercial vehicles may not use the far-left lane from milepost 205.5 to 221.0 except to pass (C.R.S. 42-4-1014).
• From September 1 through May 31, commercial vehicles with a declared GVWR of 16,001 lb or more must be equipped with chains or approved traction devices on I-70 west of Morrison, which includes the tunnel (C.R.S. 42-4-106(5)(a)(I)(C)).
• The tunnel saves 9.1 miles compared with US 6 over Loveland Pass (CDOT).

The tunnel sits inside Colorado's seasonal chain corridor for trucks. From September 1 through May 31, a commercial vehicle with a declared gross vehicle weight rating of 16,001 lb or more on I-70 west of milepost 259 (Morrison) must be equipped for snow in any weather, and CDOT and the State Patrol enforce that as a duty to carry chains or approved alternate traction devices (C.R.S. 42-4-106(5)(a)(I)(C); CDOT).

When CDOT posts the Commercial Vehicle Chain Law (CDOT calls it Code 18), every vehicle with a GVWR or GCWR of 16,001 lb or more, commercial or recreational, must have chains or approved traction devices on at least four drive tires, or on all of them if it has fewer than four. A bus chains two (2 CCR 601-14, Rules 5.01 and 5.02). While the chain law is on, those vehicles stay in the right lane and may pass only around a stalled or slower vehicle (Rule 5.05). Under the 2026 printing of the Colorado Revised Statutes, a commercial vehicle that violates a chain restriction faces a $500 fine plus a $78 surcharge, rising to $1,000 plus $156 if the violation closes a travel lane (C.R.S. 42-4-1701(4)(a)(I)(F)).

A second rule covers every vehicle on the busiest part of that stretch. On I-70 between Dotsero (milepost 133) and Morrison, from September 1 through May 31, every motor vehicle needs chains, an approved traction device, or tires with at least 3/16 inch of tread that bear the mountain-snowflake or M+S mark or are rated all-weather (C.R.S. 42-4-106(5)(a)(I)(B) and (C.5)). CDOT's storm levels for passenger vehicles are Code 15, the traction law, and Code 16, the chain law (CDOT).

CDOT does not close the tunnel on a schedule. It stops traffic at the portals for crashes, fires, avalanche control on the approaches (daylight hours in winter), and backups. With no shoulders inside, CDOT will not let a queue sit in the bores where crews could not reach a fire or a medical call, so it holds inbound traffic until the queue clears. This is called metering. Holds usually average about 20 minutes, and CDOT measured the actual delay at about 3 and a half minutes because released traffic catches up with the slow queue ahead. Eastbound metering is most common on Sunday afternoons, and the heaviest traffic runs January through March and in July and August (CDOT metering page).

When Loveland Pass is closed, CDOT also stops all other traffic, usually at the top of the hour, to escort waiting hazmat loads through. Those holds last about 15 minutes (CDOT).

As of September 2026, CDOT is running weekday single-lane closures, Monday through Thursday, on I-70 between Silverthorne (Exit 205) and the tunnel for a culvert repair project, with a 45 mph work-zone limit. CDOT expects to finish in fall 2026 (CDOT project page).

Colorado drilled a pilot bore first and finished it in 1964. Work on the westbound bore began March 15, 1968, and it opened to two-way traffic on March 8, 1973. During construction it was called the Straight Creek Tunnel, after the valley at the west portal. The legislature named it for President Dwight D. Eisenhower in 1972 (CDOT).

One bore carrying both directions turned into a bottleneck for ski and summer traffic almost at once. Mining on the eastbound bore began August 18, 1975, and it opened December 21, 1979. It honors Edwin C. Johnson, a Colorado governor and U.S. senator who fought for an Interstate across the state (CDOT).

Both bores hit weak rock and shifting loads the designs had not counted on, and the work ran years long and over budget. CDOT's own history quotes a veteran highway engineer: "We were going by the book, but the damned mountain couldn't read." The first bore cost $108 million, about 92 percent of it federal aid. Three workers died building it and four more died on the second bore (CDOT).

CDOT says the tunnel saw two to three fires a year after it opened. A fixed water-deluge fire-suppression system, a $25 million project that included a $10 million federal TIGER grant, was built in 2015. CDOT says it will not completely put out a vehicle fire; it buys time for responders to get close (CDOT). By March 8, 2023, its 50th anniversary, CDOT counted 434,431,100 vehicles through the two bores.