Highway 140 Into Yosemite and the Slide It Detours Around

Highway 140 is the low-elevation route into Yosemite from Merced and Mariposa, following the Merced River canyon up to El Portal and the park's west entrance. For many years one section of it has not really been the highway at all, but a temporary bypass around one of the Sierra's most persistent rockslides. If you are planning a Yosemite trip from the valley, especially with a trailer or motorhome, it is worth understanding.

What happened, and where things stand

Caltrans describes the section of SR 140 within the Ferguson Slide area as damaged by the rockslide, with motorists using a temporary bypass route. It says access to Yosemite National Park and the community of El Portal has been severely restricted, causing significant economic losses, and that restoring the route would end the detours and extended commutes for residents, businesses and workers.

The repair is in two phases. The first, completed in summer 2024, removed about 320,000 tons of slide material, installed cable net drapery to limit further rockfall and drilled 22 rock drains into the slide. Crews used remote-controlled equipment and real-time slide monitoring to work safely in the slide zone.

The rock shed, 2026 to the early 2030s

The second phase is a 675-foot rock shed built on the highway's original alignment, a concrete structure that lets falling rock pass over the road. Caltrans lists construction as beginning in summer 2026 and lasting about five years. The shed will be made of 11 precast concrete segments with a 40-foot interior width, anchored by hundreds of rock anchors and micro piles, and Caltrans says it will be the first rock shed built by jacking precast segments around a curve.

For drivers, that means years of an active construction zone on the main route into the park. Under Vehicle Code section 42009, fines for listed violations, such as ignoring traffic control devices, unsafe passing or failing to yield, go up in highway construction and maintenance areas while traffic is regulated or workers are present.

What it means for RVs and trailers

Caltrans states the purpose of the project as restoring a reliable SR 140 that stays open to vehicle and bicycle traffic, including large commercial trucks, emergency vehicles and recreational vehicles. The temporary bypass is not the full highway, so before you take a motorhome or a long trailer this way, check the current vehicle length limits and conditions with Caltrans District 10 or QuickMap. If 140 does not suit your rig, the other western approaches are SR 41 from Fresno and Oakhurst and SR 120 through Big Oak Flat. SR 120 east over Tioga Pass is the one that closes every winter, as our guide to seasonal pass closures explains.

Driving the canyon

• Expect delays at the bypass and the work zone, and build them into your arrival time at the park.
• Obey every signal, sign and flagger even when the lane ahead looks clear.
• Watch for rock on the road, particularly after storms, and use turnouts to let faster traffic by on the narrow canyon sections.
• Fill up in Mariposa or before; services in the canyon and park are limited.

Coverage questions on a Yosemite trip

A motorhome is commonly insured on its own policy rather than as an add-on to your car's, and a rented RV comes with a rental agreement that sets its own rules on coverage and where it may be driven; those terms vary, so read them before you leave. Liability on your car commonly extends to a trailer you are towing, while damage to the trailer itself usually needs separate coverage. Rock that falls onto your vehicle is commonly a comprehensive claim. And a breakdown or tow in the canyon with a large vehicle can be costly, since many roadside programs treat motorhomes and trailers differently from cars. You can have your car, trailer or RV coverage reviewed before the trip.