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By Dave Boyce
Almanac Staff Writer
Bikes heading westbound on Sand Hill Road as they approach Interstate 280 have the option of merging with traffic into a bike lane that, as it crosses the freeway, centers the cyclists in between two lanes of traffic, one headed for the freeway and the other up Sand Hill and on into Woodside.
A similar design is under consideration for Alpine Road as it approaches I-280, the intersection where, on Nov. 4, Los Altos Hills cyclist Lauren Ward died after a collision with a tractor trailer.
The hundreds of westbound bicycles that traverse the Alpine Road intersection every day have been making do without a bike lane. That would change with the implementation of any of four proposed designs now being looked at by the San Mateo County Public Works Department and the California Transportation Department.
Go to this link to view the four designs. Each inserts a bike lane between the lane for I-280-bound traffic and the lane into Ladera as Alpine Road passes under the freeway. The differences lie in where bikes weave into traffic and the markings indicating the bike lane.
The Almanac spoke with Assistant Civil Engineer Robin duSaint of the county public works department about the four options.
■ Option D-1 has bikes merge with vehicle traffic after the stop sign. The bike lane boundaries are marked by dotted lines at first and then solid lines further west.
■ Option D-2 has bikes split the traffic lanes and weave into traffic well before the stop sign. The boundary lines are solid for the bike lane.
■ Option D-3 is like D-1 as to where it would merge bikes and traffic, and like D-2 in that it uses solid lines to mark the bike lane. But D-3 adds pavement cross-hatching and two road signs: one ordering vehicles to yield to bikes, and another forbidding vehicles already committed to the southbound freeway to cross the bike lane and head into Ladera.
■ Option D-4 resembles D-3, including the signs, but with a substantially longer and continuous bike lane with a painted pavement.
"We prefer D-3," Ms. duSaint said. Why? Because D-3 would merge bikes after the stop sign, the merging traffic is moving more slowly. D-2 has the merge happening before the stop sign; traffic headed to I-280 north from Alpine Road has a straight shot to the onramp, Ms. duSaint noted.
Corinne Winter, executive director of the Silicon Valley Bicycle Coalition, said she agrees that the speed of motor vehicles when merging with bikes is a major concern.
Moving from light to dark is another potential problem. With the current D-3, cyclists move west from the stop sign in full daylight, but merge with motor traffic in the relative darkness under the freeway overpass.
The bicycle coalition prefers a combination of D-3 and D-4's painted bike lane, Ms. Winter said.
Records of the California Traffic Control Devices Committee show ongoing experiments with colored bike lanes, including in San Francisco.
To apply color at Alpine Road, San Mateo County would have to ask the committee, Ms. Winter said, adding that while she would like the county to apply, it should not delay a fix to the intersection.
The bottom line, she said, is safety. The intersection "should be safe enough for 8-year-olds to ride their bikes across," she said.