Stand at the corner of Tartan Trail Road and Crystal Springs Road this week and you'll see two separate town projects trying to use the same twenty feet of pavement. One is a bridge. One is a trail. Neither has anything to do with the other on paper. In practice, this single stretch of road is now the pinch point for both.
Most of Hillsborough has heard about one closure or the other by now, usually through a town e-blast or a sign posted at a trailhead. What's easy to miss, unless you're actually tracing the detour routes on a map, is that they land on the same road at the same time of year. If you've been treating them as two unrelated inconveniences, it's worth understanding how they actually connect, because it changes which routes are genuinely open right now and which ones just look open.
The bridge that isn't optional
The Tartan Trail Road Bridge crosses San Mateo Creek, and the Town of Hillsborough has been blunt about what that bridge means to the neighborhoods on either side of it. In its own project notice, the town called it a critical access point into Town for many residents. The bridge and roadway have been compromised by erosion, pavement failure, and subsurface issues tied to a failed PG&E conduit trench beneath the road. This isn't routine maintenance deferred a season too long. It's an emergency design-build repair, and the town treated it that way, awarding the contract to Power Engineering Construction Company back on November 10, 2025, then working through permitting agencies to avoid further delay.
The town's published schedule anticipated construction beginning as early as June 3, 2026, pending final regulatory authorizations, with a full 24-hour closure required for the duration of the work. Based on that timeline, Hillsborough is likely now several months into a closure that has no fixed end date. The town's most recent estimate puts the project running through Winter 2026, which means there is no through access between Tartan Trail Road and Crystal Springs Road until then.
The detour the town has mapped out runs via Crystal Springs Road, Skyline Boulevard, Golf Course Drive, Hayne Road, and Black Mountain Road. That's a wider loop than the direct route it replaces, and it funnels a meaningful share of that displaced traffic straight onto Crystal Springs Road.
The trail that closes for three days, not three seasons
Separately, and on a much shorter timeline, San Mateo County Parks has scheduled a closure of the Sawyer Camp segment of the Crystal Springs Regional Trail from the evening of Monday, September 7 through Thursday, September 10, while crews replace a culvert. Three days, not three seasons. But Sawyer Camp isn't a minor path. It's a paved, six-mile out-and-back that traces the shoreline of Lower Crystal Springs Reservoir, and San Mateo County Parks itself describes it as more used than any other trail in the county park system. It's wheelchair accessible, popular with joggers, cyclists, and equestrians, and it draws people from well beyond Hillsborough's borders on a typical weekend.
The detail that matters here, and the one that doesn't show up if you only read the two closure notices separately, is where the Sawyer Camp segment actually starts and ends. It runs from Hillcrest Boulevard on the north down to Crystal Springs Road on the south. Crystal Springs Road isn't just a detour route for displaced drivers this fall. It's also the southern trailhead for the very trail that's closed for its own construction this same week.
One road doing two jobs
That's the part worth sitting with. For three days starting September 7, Crystal Springs Road absorbs traffic detoured off Tartan Trail Road at the same moment its own southern trailhead access to Sawyer Camp is shut down for a separate crew's work. It isn't that Hillsborough has two closures this fall. It's that both closures point at the same short stretch of road, and the town's own language about that road as "a critical access point into Town for many residents" applies just as much to the walkers and cyclists trying to reach the reservoir as it does to drivers trying to get home.
For anyone who treats Crystal Springs Road as the quiet way around the Tartan Trail Road mess, this week is the wrong week to test that theory. Once the culvert work wraps up after September 10, the trail access reopens, but the bridge detour keeps running the same loop through Skyline Boulevard, Golf Course Drive, Hayne Road, and Black Mountain Road for months longer.
Golf Course Drive is worth a second look too, since it's one of the streets absorbing that detour traffic. It's the same road that runs past Crystal Springs Golf Course, which hosted the 70th annual Hillsborough Concours d'Elegance this past June, drawing collector cars and crowds from across the region for a weekend built around the fairways. That event is done for the year, but it's a reminder that this stretch of road already carries more than its share of traffic on a normal summer weekend, before you add a bridge detour on top of it.
What this actually looks like week to week
Two different clocks are running here, and it helps to keep them separate:
- This week only (September 7 through 10): Sawyer Camp Trail's southern access at Crystal Springs Road is closed for culvert work. If your regular walk, run, or ride starts from that end, you'll need to pick it up from the Hillcrest Boulevard side instead, or wait until the culvert work finishes.
- Now through Winter 2026: The Tartan Trail Road Bridge stays fully closed to through traffic. The detour, Crystal Springs Road to Skyline Boulevard to Golf Course Drive to Hayne Road to Black Mountain Road, is the only official route between the two sides of that closure, and it's the one to plan around for the rest of the year, not just this month.
The town has said it will keep posting updates to its Current Projects page and through e-blast notifications as the bridge schedule firms up, so that Winter 2026 estimate is a target, not a guarantee. Anyone whose daily route depends on that stretch of road is better off checking the town's project page directly than relying on word of mouth about when it might reopen.
None of this changes how Hillsborough looks from the street. The half-acre lots, the mature trees, the quiet that comes with a town built almost entirely of single-family homes on winding roads, that's all still there. But the roads themselves are part of what makes a town like this work day to day, and right now one of them is being asked to do more than it usually does. Knowing which detour is temporary and which one is here through winter is the difference between a minor reroute and a genuinely different commute for the rest of the year.
If you're weighing a move within Hillsborough, or trying to understand how a property's location relative to Crystal Springs Road or Tartan Trail Road might affect day-to-day access during this stretch, that's exactly the kind of on-the-ground detail worth talking through with someone who tracks this town closely. Lana Morin Pierce works this market year-round and can walk you through what these changes mean for a specific address. Book a consultation when you're ready to talk specifics.
