About 70 local residents, most from Ladera and Stanford Weekend Acres, gathered Nov. 1 at Woodland School in Ladera for a third presentation, sponsored by the San Mateo County Public Works Department, on addressing congestion and speed problems on the two-mile stretch of Alpine Road that connects these two unincorporated communities.
Residents of Weekend Acres, nestled in a hollow bordered by Alpine Road and San Francisquito Creek and the Stanford golf course, face daunting traffic when trying to enter or leave their neighborhood. Imagine 150 households served by just two driveways Stowe Lane and Bishop Lane connecting to an arterial road that commuters and others jam bumper-to-bumper twice a day and the rest of the time travel at speeds consistent with an expressway, despite darkness and poor lines of sight.
A Weekend Acres resident told the Almanac earlier this year that he had between two and four seconds, depending on traffic volume, to join the flow when leaving the community on a typical morning. In Ladera, the problem is not as dire, but continuous traffic and poor sight lines complicate leaving the neighborhood.
Based on feedback from the meetings, county public works staff will prepare a report to serve as a reference for addressing the problems over the coming years.
At the meeting, traffic engineering consultant Adam Dankberg gave a presentation with 40 slides, followed by small-group discussions and a question-and-answer session.
Click here to download the presentation.
Signal or roundabout
During Phase 1 the next year or two the county could take low-cost and easily implemented steps such as reducing the speed limit to 35 mph throughout the corridor, installing digital speed-limit signs, using more green paint in bike lanes at places of potential conflict with vehicles, and adding "Keep clear" markings across the pavement at problematic intersections, Mr. Dankberg said.
The focus of Phase 2, he said, would be the major intersections and how to regulate them, whether with roundabouts or traffic signals -- big-ticket items that involve federal grants and careful analysis by the California Department of Transportation.
Ladera residents have shown they favor roundabouts at La Mesa and/or La Cuesta drives in Ladera over traffic signals, Mr. Dankberg said. While roundabouts take up more space and are more expensive to put in, they tend to slow traffic and reduce accidents, he said.
Roundabouts are not a bicyclist's best friend, and cyclists make heavy use of Alpine Road. The absence of bike lanes requires cyclists to enter a roundabout as if they were vehicles. Roundabouts in Ladera could accommodate cyclists uncomfortable with joining the flow of traffic with an alternative directing them to a crosswalk a short distance away, Mr. Dankberg said.
At the Interstate 280 interchange, roundabouts at the two off-ramps would be less viable, he said. For one thing, they would be two lanes, something potentially confusing since Bay Area drivers seldom encounter them, he said. A one-lane roundabout would be "total gridlock," he said.
Roundabouts at I-280 would be near their handling capacity in 20 years and begin to create backups, he said. They abet a continuous flow of traffic, a pattern unhelpful to Weekend Acres residents trying to get in and out of their neighborhood. And two-lane roundabouts run between $8 million and $12 million, Mr. Dankberg said.
Traffic signals at these intersections would cost between $1 and $2 million and not lose their effectiveness as time passed, he said. They also create platoons, creating breaks in traffic to allow Weekend Acres residents to have less of an adventure entering and leaving their neighborhood. Signals at I-280 would also include bike lanes.
On the downside, signals do not reduce vehicle speed and nor do they increase safety in the way that roundabouts do, he said.
No more tunnel
A traffic signal at the I-280 intersection closest to Ladera could include a benefit for cyclists coming from Ladera. As cyclists approach I-280, they cannot ignore vehicles approaching from behind headed to the southbound freeway, their speed increasing in anticipation of the on-ramp. There's green paint on the pavement, but that's no guarantee of safe passage.
With a signal, engineers could eliminate that anticipation on the part of drivers by removing the on-ramp and requiring them to stop and turn left to the southbound ramp on the other side of Alpine Road.
For cyclists as well as pedestrians, this change would create an uninterrupted path along Alpine between Ladera and the far side of the I-280 interchange. It would also eliminate the uninviting low-roofed pedestrian tunnel now under the southbound ramp, Mr. Dankberg said.
It's a tradeoff, he said. More safety for pedestrians and cyclists in exchange for some delay for vehicles by requiring a left turn to get to a southbound on-ramp.