What the Diablo Road Lane Closures Are Building, and the Trails Already Open Across the Road

The flaggers on Diablo Road are working on the last piece of a trail system. Most of the 2.1-mile paved path between Green Valley Road and Blackhawk Road is already in place. So are more than five miles of public trail in Magee Preserve, along the road's south side. What is left is the 0.9-mile segment in the middle, and the Town of Danville expects lane closures there to last "likely through November, weather permitting."

What the work zone looks like this fall

The Town's October 15 construction update says the big structural work is done. The major retaining walls are finished, and so is the work inside Green Valley Creek. Crews are now on the strip between the creek and Diablo Road, installing drainage, preparing the trail foundation, and paving the path. Guardrails along the road and handrails along the trail still have to go in.

Closures stay in the same spot, from 8:30 a.m. to 5 p.m. The Town says some days may not need a closure at all. Much of what remains still involves large trucks and heavy equipment working along the roadway.

Those hours are shorter than summer's. The Town's June 12 traffic advisory set weekday traffic control from 7 a.m. to as late as 6 p.m., June 15 through September 15. That phase covered wall construction near the creek between Fairway Drive and Alameda Diablo, with one-way traffic between Clydesdale Drive and Alameda Diablo. The fall window starts an hour and a half later and ends an hour earlier.

Three segments make one route

The finished trail is three segments built by different parties at different times. The Town's groundbreaking announcement from October 2025 and its segment summary lay them out from west to east:

The Town's segment is designed as an 8-foot paved path with 2-foot gravel shoulders. It sits 4 to 5 feet from Diablo Road with a physical barrier between the path and traffic.

The west end is where the route switches sides of the road. A June 2026 Town Manager update says the project includes a new HAWK signal, a high-intensity activated crosswalk, at Diablo Road and Fairway Drive. It "will allow users to safely cross by stopping traffic on demand," linking the new south-side path to the Barbara Hale Trail on the north side. At the far east end, the Magee Preserve design approved in 2019 calls for a crosswalk across Blackhawk Road at the project entrance. It connects the Magee path to an existing paved trail on the north side of Blackhawk Road.

The trails on the far end opened first

On June 24, 2025, the East Bay Regional Park District held a ribbon-cutting that formalized public access to more than 3.5 miles of trail on the 381-acre Magee Preserve property. Those trails connect to the northern ridge of Sycamore Valley Open Space Regional Preserve, as the Park District reported at the time. The Park District holds the trail easement. The open space itself is owned and maintained by the Wiedemann Ranch Geologic Hazard Abatement District.

In August 2026, Save Mount Diablo opened two more. The Art Bonwell Trail is named for one of the organization's co-founders. The Do'-yum'-bel'-le Vista Trail takes its name from the Bay Miwok name for Mount Diablo, chosen after conversations with local tribes, and the trail has broad views of the mountain. Save Mount Diablo's announcement says the two trails add more than two miles to the 3.5-plus miles open since June 2025.

The Art Bonwell Trail was laid out with the Diablo Road path in mind. Sean Burke, Save Mount Diablo's Land Programs Director, told the organization's blog that Bonwell had been a cyclist:

"one of our founders, Art Bonwell, who was an avid supporter of ours as well as a cyclist, making that trail where it parallels and ties into the new Diablo Road bike trail a no-brainer"

Executive Director Ted Clement thanked Davidon Homes for donating the trails easement. He also credited Dave Hammond and the Trail Dogs volunteer crew, along with the Park District and the Town of Danville. Athenian High School students helped build trails in the preserve.

So the 0.9 miles under construction now will join a road-side path to a trail system that opened in stages over the past 16 months.

Why the middle came last

The order comes down to terrain. The Town's project page says Danville's Townwide Trail Master Plan, adopted in 1989, called for closing the gap between the Barbara Hale Trail and access to Mount Diablo State Park. The page calls this segment "one of the most difficult to construct" because it had to cross a creek and hilly ground on what was then the privately owned Magee property.

What opened the way was the Magee Preserve approval. The 69-home project dedicated 93 percent of the 410-acre ranch to open space. It required the developer to build the flatter eastern segment and to give the Town a public easement for the harder western one. Danville voters protected the 381 acres through Measure Y in March 2020, which allowed development on 29 acres. The Town says it had about half the construction money when the project was approved and secured the rest by summer 2021. The 2025 groundbreaking release lists a $5.2 million budget, with $4.7 million from the Contra Costa Transportation Authority's Measure J transportation sales tax.

At that ceremony, Mayor Renee Morgan said, "Over 36 years ago, we were standing here, envisioning this trail," as the Town's release recorded.

The creek that made this segment hard to build also slowed it down this year. Construction started in early March 2026. The June Town Manager update describes two delays. Crews had to wait for nesting birds to fledge before getting state Department of Fish and Wildlife approval, and PG&E had to relocate utility guy wires inside the construction area before wall work in the creek could start. Those walls are now done, which is why the October work has moved up to the roadside.

The Town has said construction will continue in phases through December 2026. The Town posts message boards 72 hours before scheduled work. Questions go to Transportation Manager Soren Fajeau at the Town of Danville.

Using the open pieces before the paving is done

Until the Fairway Drive crossing and the middle segment open, the preserve trails are reachable another way. The Park District lists two staging areas for Sycamore Valley Regional Open Space Preserve, one on Holbrook Drive and one on Sherburne Hills Road. The Magee Preserve trails connect into the preserve's northern ridge.

The mountain has its own fall calendar. Mount Diablo State Park's gates open at 8 a.m. and close at sunset, so the shorter days cut into evening access. A July 2026 State Parks release lists the South Gate entrance at 2675 Mt. Diablo Scenic Boulevard and a $10 day-use vehicle fee. Coming up on the Save Mount Diablo events calendar and the State Parks Mount Diablo page:

1. October 24, 9 a.m. to noon: Borges Ranch Fall Hike with Save Mount Diablo, listed as sold out with a waitlist.
2. October 25, 9 a.m. to noon: "The Morning Side of Mount Diablo from Morgan Territory."
3. October 25, 3 to 6 p.m.: Halloween Hike on Devil Mountain, an easy two-mile walk with tarantula-themed natural history. It starts at the Mitchell Canyon Visitor Center on the Clayton side, where the listing shows a $6 vehicle fee, or $5 for seniors.
4. November 7, 9 a.m. to noon: Black Diamond Mines Autumn Hike.
5. November 11: "Wonder Hike" listed by State Parks.
6. December 6, 9 a.m. to noon: "Winter's Adaptations in the Oak Savanna."
7. December 11, 9 a.m. to noon: "Hit the Trails – Mountain Biking," from Smith Canyon into Curry Canyon.

Event capacity changes, so check each listing before you go. For lane closures, the Town's project page has the newest update.

For more on the communities around this corridor, see our guides to Danville and Blackhawk. If you're weighing how a finished trail at the end of your street fits into a future move, Armario Homes knows this stretch of Diablo Road well. Schedule a Free Consultation and we'll talk through what's changing near your home.