To Reduce Congestion, City of Mill Valley Will Fine-Tune Timing of Traffic Lights

In an effort to combat ongoing traffic congestion along two of its major roadways, the City of Mill Valley and Caltrans are implementing a major change to the timing of nine traffic lights from the Camino Alto and Miller Avenue intersection out to East Blithedale Avenue, Tiburon Boulevard and Highway 101.

The new timing, set to begin May 5, is expected to reduce backups along those roads by lengthening the time that lights stay green, particularly for outbound drivers along Camino Alto and East Blithedale. As a result of the changes, some side streets will experience slightly higher delays depending upon the time of day.

"The existing traffic signal timing along those corridors hasn't been looked at since 2001," Jill Barnes, the City's Director of Public Works, told the City Council at its April 21 meeting. "We want to improve mobility along those corridors, and reduce greenhouse gas emissions and fuel consumption as a result."

During the first two weeks of the new traffic light timing, City staff will closely monitor the new timing and make adjustments to respond to the City's particular traffic patterns. To assist in those adjustments, residents and drivers are asked to click here to submit info on their own experience with specific details about where they've hit delays and back-ups and to suggest changes. City staff will check this input regularly and make adjustments in response.

In addition to reducing traffic delays along the East Blithedale and Camino Alto corridors, the City hopes the changes will reduce the greenhouse gas emissions that result from traffic backing up along the way. Those goals were identified in the City's recently adopted Mill Valley 2040 General Plan.

"I've pushed for an update to our traffic signal timing since I was elected in 2007," Mayor Stephanie Moulton-Peters said. "I'm very glad DPW Director Barnes won the grant for these much needed improvements and that we will see them come to fruition this year. This is a major step in Mill Valley's effort to address congestion - and there are more steps planned in the future."

The City's efforts to alter traffic light timing dates back several years and were kick-started by a successful application to obtain grant funding via the Program for Arterial System Synchronization (PASS), which provides technical assistance to Bay Area agencies to help improve the safe and efficient operation of certain traffic signal systems and corridors. The Metropolitan Transportation Commission has allocated approximately $2 million in federal funds for the PASS, and the City obtained services and equipment equal to $50,000.

The contribution allowed the City to work with traffic consulting firm Iteris to do traffic counts along East Blithedale and Camino Alto on days when school was in-session and on weekends and to review the equipment and existing signal timing at each of the nine intersections. As a result of those counts, Iteris recommended signal-timing changes and the installation of three new GPS clocks along the corridor.

Synchronization
A key first step in the new program is simple but critical, according to Barnes: getting the six signals along Camino Alto and East Blithedale to talk to one another. Here are the nine signals that are part of the new program:

1. Tiburon Boulevard (SR-131) at Redwood Highway/Frontage Road
2. East Blithedale Avenue/Tiburon Boulevard (SR-131) at US-101 northbound ramps
3. East Blithedale Avenue at US-101 southbound ramps
4. East Blithedale Avenue at Tower Drive/Kipling Drive 
5. East Blithedale Avenue at Lomita Drive/Roque Moraes Drive
6. East Blithedale Avenue at Camino Alto
7. Camino Alto at Sycamore Avenue
8. Camino Alto at Redwoods/Pedestrian Crossing
9. Camino Alto at Miller Avenue

Without the ability of those lights to talk to one another, adjusting one set of lights wouldn't make a dent in traffic congestion unless the other set is adjusted as well. 

"It hasn't been a very reliable system overall because we haven't had a very good way for the two different systems to work together," Barnes said.

For instance, Barnes said staff had noticed that whenever a seasonal change such as Daylight Savings Time began, the systems would go out of sync with one another and delays would worsen. According to Barnes, the most acute issue at times was the fact that the adjacent traffic lights on East Blithedale at Kipling Drive and at the southbound Hwy 101 on- and off-ramps were often out of sync.

The installation of new GPS clocks - one on Camino Alto and two along East Blithedale - in the weeks leading up to May 5 will change that, David Parisi, the City's traffic consultant, told the Council.

"Now we won't see clocks drifting off from one another," he said.

Timing Changes
Once the communication between the lights is established, the nine-intersection system can then be synchronized to adjust accordingly during peak traffic times - and that's where the longer green lights (and longer red lights for side street drivers) kick in.

The City currently has its own traffic lights coordinated along East Blithedale, Miller and Camino Alto avenues during the morning and evening commute periods. During non-commute hours, the timing of the red and green lights at those intersections has been independent and derived from cars setting off sensors in the roadway. That system has allowed cars coming out of side streets to see shorter wait times.

In addition to traffic light timing coordination in the morning and evening commute, the City is implementing coordination during mid-day and school pick-up times. For instance, according to David Parisi, while the series of traffic lights on Camino Alto and up to East Blithedale at Lomita Drive have been coordinated between 7 a.m. and 9 a.m. and then again between 3 p.m. and 6 p.m., they will now also be coordinated from 11:30 a.m. to 1:30 p.m. and from 1:30 p.m. to 3:30 p.m. as well.

"Now you'll see more hours of coordinated traffic lights," Parisi said.

Barnes said that it is critical to implement the changes while school in-session this term so that staff can observe traffic and make necessary adjustments during days when traffic circulation is typical of a regular weekday.

The City also hopes to address the steady traffic along the City's major roadways on both Saturday and Sunday. For instance, the traffic studies indicated that traffic volumes on southbound Camino Alto jump to 693 vehicles per hour at 10:30 a.m., up to 865 vehicles per hours by 12:30 p.m. and drops back to 680 vehicles per hour by 4:45 p.m.

"We have a near-constant high peak of traffic on weekends," Parisi said.

As a result, traffic light timing program is expanding from the current 11 a.m.-1 p.m. on weekends to 10:30 a.m.-4:30 p.m. The extended green times that result from the coordination also account for all modes of transit, giving pedestrians, bicyclists and those with disabilities more time to cross, Barnes said.

Barnes plans to go back to the City Council with a report based on studies of the traffic light timing before and after the changes, identifying the changes in both traffic flow and greenhouse gas emissions as a result of the new traffic signal timing.

Once the changes are implemented on May, the City welcomes your feedback. Please click here to provide info on your own experience driving along the East Blithedale Avenue and Camino Alto corridors.

"We will definitely be making adjustments along the way in those first few weeks," Barnes said.