Faced with thickening traffic jams throughout its expressway network, Santa Clara County officials are considering a range of long-term projects that would add driving lanes and under- or overpasses to segments of particularly busy roads, including Page Mill Road and Foothill Expressway.

At the same time, local and regional transportation officials are backing away from a prior proposal to install traffic lights on the chronically congested interchange of Interstate 280 and Page Mill Road, where lines of stationary southbound cars routinely stretch past the off-ramp and onto the highway proper. The plan, which has been in the works since 2011 and which has the support of Caltrans (the state Department of Transportation), is now back in the slow lane after opposition from Los Altos Hills, where residents and council members vehemently criticized it in recent months. The proposed traffic signals will now be a part of a broader study of the Page Mill corridor.

The recent developments around the highway interchange underscore the steep political challenges transportation officials are facing as they look for ways to increase capacity and traffic flow on the county's expressways, a system created in the 1960s that is used daily by about 55 percent of Santa Clara County residents, according to Dawn Cameron of the county's Roads and Airports Department. The department is now working on updating Expressway Plan 2040, a document that will evaluate possible changes to expressways, including the widening of Page Mill from four lanes to six and grade-separating Foothill Expressway so that it dips under Arastradero Road.

Both expressways are already facing heavy traffic, which is expected to get worse in the years to come. The Page Mill-Oregon expressway currently accommodates about 134,000 vehicle trips per day, making it the sixth busiest in the network. But unlike the busiest expressways — Capital, Lawrence and San Tomas — it is a four-lane road (others have six or eight lanes), which further exacerbates the congestion. The four-lane Foothill Expressway has about 94,000 vehicle trips per day.

Furthermore, both expressways include intersections with the worst possible traffic conditions, known as "level of service F." This means cars are often forced to wait through several traffic-light cycles before they clear the intersection. The intersection of Foothill Expressway and Page Mill Road (which becomes Oregon Expressway east of El Camino Real) now experiences the third-highest level of delay in the entire expressway network during both the morning and the evening commute periods, with an average of 118.9 seconds.

"Traffic volumes are returning to the great pre-recession levels, leading to increasing traffic congestion throughout the expressway network," Cameron told the Palo Alto City Council during a June 16 presentation.

Things are expected to get much worse by 2025, when half of the expressway system is expected to drop to service level "F" and when half of all the intersections are projected to function at the lowest level of service.

As part of its environmental analysis for a new expressway plan, the county is exploring various long-term projects with local jurisdictions. Some of the options include an underpass at the Foothill and Page Mill intersection; the widening of Page Mill from four to six lanes west of Foothill; and grade separation of Foothill at Arastradero Road, near Gunn High School. The lattermost intersection is projected to drop to service level "F" by 2025.

Cameron told the Palo Alto council that when it comes to the busy intersection of Page Mill and Foothill, grade separation is the only way to significantly improve the traffic flow.

"We can't fix that without grade improvements," Cameron said. "The 'F' is so deep and is projected to get so much worse."

These alternatives will be further evaluated in an update of the county's General Plan's section known as the "Circulation and Mobility Element." County officials solicited comments about the scope of the element's environmental-impact report in June and have begun to put together the document.

But even after the plan is complete, the county will have to surmount significant hurdles to make the needed improvements. This includes identifying funding sources for the projects (the expressway system does not have a dedicated funding source) and winning political support for these ambitious and highly visible projects.

The latter challenges were highlighted in the recent battle over traffic signals at the Page Mill Road interchange. In March, hundreds of Los Altos Hills residents signed a petition challenging this project, which has been in the works since 2011. About 70 attended the March 20 meeting of the City Council to urge opposition to the plan.

"We are deeply worried that the signalization project would jeopardize our safety, further erode our rural environment and negatively impact our property values," the petition stated. "The implementation of the signalization project would result in a number of risk factors affecting not only the neighborhood in the vicinity of the interchange but also numerous other areas of Los Altos Hills."

Faced with the swell of opposition, the county and Caltrans agreed recently to postpone the project and to do further analysis of the corridor before proceeding with the changes. On June 24, the county's Board of Supervisors approved a consulting contract to make improvements on this interchange "upon achieving consensus among the cities and county on an overall concept plan." Rather than proceeding with the traffic signals, the purpose now is to come up with a broader design "that can be implemented in a phased approach" and that will be integrated into the project list in Expressway Plan 2040, according to a county report.

At a May 15 council meeting, Los Altos Hills Mayor John Radford lauded the change in plans.

"We've gone from two months ago having 500 residents sign a petitions saying we didn't know what we're talking about to now a plan that's systematic, that involves all the partners, where Los Altos Hills has a significant partnership in the outcome," Radford said. "It recognizes that the solution at 280 and Page Mill is not simply a set of lights but a much broader and integrated plan that we have looked at before."

The consultant hired by the county will also look at possible improvements to the steep, short and frequently backed-up Page Mill and Alma Street interchange, which was constructed in 1954 and which continues to concern Palo Alto officials. At the June 16 council meeting, Councilman Larry Klein characterized the ramp as "an accident waiting to happen."

"As long as I've lived here, I've been concerned about the ramp from Alma onto Page Mill-Oregon," Klein said, noting the "very short roadway" and the "very limited sight lines" on the ramp. "I've always been concerned that there's going to be some major accident at some point."

Though the county estimates the cost of redesigning and reconstructing the ramp to be about $130 million, regional and local officials are thinking of other ways to make the intersection safer, including traffic-signal improvements and realignments of other existing roads to steer drivers away from the Alma ramps. The city would have to contribute $60,000 for the county to study near-term improvements to the ramp system, Palo Alto's Chief Transportation Official Jaime Rodriguez told the council on June 16.