REPORT TO BICYCLE AND PEDESTRIAN ADVISORY COMMITTEE
SUBJECT
Title
Traffic Calming/Lower Motor Vehicle Speeds and Speed Limits (He)
Report
BACKGROUND
In August 2023, Bicycle and Pedestrian Advisory Committee (BPAC) Member Kratz requested BPAC discuss Traffic Calming on Benton Street (Attachment 1) and how to Lower Motor Vehicle Speeds and Speed Limits (Attachment 2).
DISCUSSION
Below is a summary of responses to the requests from Member Kratz.
1. Provide Traffic Calming on Benton Street from Lawrence Expressway to Montague Expressway.
Benton Street is an east-west roadway in Santa Clara that stretches from the west near Sunnyvale to the east through El Camino Real and ending at the Santa Clara Caltrain Station. Benton Street, between Lawrence Expressway and San Tomas Expressway, is generally a 30-mph 4-lane roadway. This segment carries a daily traffic volume of approximately 12,000 vehicles. A speed survey conducted in Spring 2023 found that 64 percent of drivers exceeded the 30-mph speed limit and the 85th percentile speed was 39-mph. The segment is adjacent to Earl. R. Carmichael Park and Santa Clara High School and it is near Central Park Elementary School. Most of the section contains residences and churches.
At the March 2023 BPAC meeting, staff presented information on the City’s Neighborhood Traffic Calming Program (NCTP) and applicable traffic calming measures that can be implemented on Benton Street. Due to being classified as a Police and Fire Emergency Response Route, only Level 1 and 2 traffic calming measures can be applied to Benton Street between Lawrence Expressway and Montague Expressway. Level 1 traffic calming measures include education, public involvement, enforcement efforts, signing, striping, parking controls, and use of the City’s speed radar trailer. Level 2 traffic calming measures include chicanes, chokers, gateways, and rumble strips. Implementation of Level 2 measures will require significant support from affected neighborhood.
In addition, since January 2023, the City has been working on the Benton Street Bikeway Study that evaluates different design options to install buffered bicycle lanes on the roadway. At the August 2023 and January 2024 BPAC meetings, the project team presented four design options to BPAC for consideration:
• Current Existing Conditions/No Build Option
• Concept A: Two Lanes with Buffered Bike Lanes, Parking on Both Sides.
• Concept B: Two Lanes with Parking-protected Bike Lanes.
• Concept C: Four Lanes with Parking removed on one side.
Concept A and Concept B both involve a “Road Diet”, which converts an existing four-lane roadway to a three-lane roadway consisting of two through lanes and a center two-way left-turn lane. On a three-lane roadway with a center left turn lane, the vehicle speed differential is limited by the speed of the lead vehicle in the through lane, and through vehicles are separated from left-turning vehicles. Studies from the Federal Highway Administration (FHWA) and Caltrans indicate a 19 to 47 percent reduction in overall crashes with implementation of a road diet. Road diets also improve safety by reducing the speed differential and reducing vehicle conflicts. Research also showed a reduction in the 85th percentile speed of less than 5-mph and in the number of vehicles speeding excessively, defined as those going over 36-mph in a 30-mph speed zone. A greater reduction in speed was observed on corridors with higher traffic volumes.
All three concepts also include lane narrowing which proposes to reduce the existing traffic lanes down to 10-11 feet wide, which brings additional safety benefits to slow vehicle speeds by 1-3 mph.
Staff plans to bring the Benton Street Bikeway Study back to the BPAC to select a preferred design alternative in Summer 2024. Should the City Council decide which bikeway design option to move forward on Benton Street, staff can evaluate other traffic calming measures (discussed in item #3 below) that can supplement the selected design alternative.
2. Investigate how the City can reduce motor vehicle speeds below current posted speed limits throughout the city.
According to FHWA, a safe speed is a travel speed that lowers the likelihood of a crash by allowing more response time and better visibility. Per California Vehicle Code (CVC) Section 22349, the maximum speed limit on a multilane highway and two-lane undivided roadway is 65-mph and 55-mph, respectively. In general, speed limits are established by conducting an Engineering and Traffic Survey (E&TS) or a prima facie zone, by considering the following:
• Prevailing speeds (or 85th percentile speeds)
• Collision History
• Highway, traffic, and roadside conditions not readily apparent to the driver
The CVC designates prima facie speed limits to govern vehicular speeds on roads that may not have speed limits. A prima facie speed limit is a default speed limit that applies under conditions when a posted speed limit is not determined based on an engineering and traffic survey such as within residential districts, business districts, senior zone, school zone, etc.
Other factors that may be considered while developing E&TS are business or residential density, pedestrian, and bicyclist safety.
Recent state legislation - AB 43, AB 1938, and AB 321 have given local jurisdictions more flexibility in setting speed limits on the local roads in three ways:
(1) The creation of new prima facie zone legislation allowing lower speed limit designations in Business Activity Districts and certain school zones.
(2) Granting local jurisdictions, the ability to further lower speed limits in certain safety-related settings relative to 85th percentile speeds measured during the E&TS process.
(3) Granting local jurisdictions, the ability to retain current speed limits or restore the immediately prior speed limit on a corridor, especially if it was raised in the past 10 years, even if the current E&TS shows a higher 85th percentile speed.
Staff will provide a more detailed verbal report on the changes in speed limit setting due to new state legislation and the next steps the City can take to reduce speed limits on certain local roadways such as the following:
(1) Review “local roads” (defined by Caltrans’s California Road System) and prima facie zones to see what speed limits can be reduced without an E&TS, especially within school zones, Business Activity Districts, and land uses that can generate a high concentration of bicyclists or pedestrians.
(2) If the road is not designated as a local roadway and not a prima facie zone, an E&TS must be performed. The City can rely on a prior E&TS conducted for the roadway to either restore or retain the previous speed limit.
(3) The City is starting to develop a Vision Zero Plan, which will include a High-injury Network analysis. This analysis will help City identify the safety corridors that have high rate of fatal or serious injury crashes and these corridors can be candidates for speed limit reductions.
The California Manual on Uniform Traffic Control Devices (MUTCD) and California Manual on Setting Speed Limits (CMSSL), which regulate and guide local jurisdictions to establish and modify speed limits on roadways, are still being updated to reflect most recent policy changes.
3. Identify potential design features to lower vehicle speeds and identify potential streets for “road diet”.
In addition to a “Road Diet” and lane narrowing, the Caltrans Traffic Calming Guide includes other potential design features that may help lower vehicle speeds. There are six major categories of these traffic calming strategies:
(1) Signs and Markings, such as vehicle speed feedback signs, in-street pedestrian crossing signs, crosswalk enhancements, and pedestrian hybrid beacons.
(2) Physical Intersection Modifications, such as roundabouts, reduce corner radii, and intersection barrier.
(3) Roadway Narrowing, such as curb extension, raised median island, and road diet.
(4) Vertical Roadway Elements, such as speed humps, speed tables, and raised intersection.
(5) Physical Roadway Segment Modifications, such as lateral shifts and chicanes.
(6) Others such as street trees and landscaping and in-roadway light.
Staff follows the FHWA guide which utilizes the annual daily traffic (ADT) volumes of a roadway to help identify a roadway that is suitable for a four-lane to three-lane road diet conversion, as discussed below:
• <10,000 ADT: A great candidate in most instances. Capacity will most likely not be affected.
• 10,000-15,000 ADT: A good candidate in most instances. Agencies should conduct intersection analyses and consider signal retiming in conjunction with implementation.
• 15,000-20,000 ADT: A good candidate for Road Diets in some instances; however, capacity may be affected depending on conditions. Agencies should conduct a corridor analysis.
• >20,000 ADT: Agencies should complete a feasibility study to determine whether the location is a good candidate.
FHWA also provides guidance on how to select candidate road diet locations:
(1) By citing road diets as a strategy in safety plans, which helps systemic identification and implementation.
(2) By evaluating all four-lane undivided roads, which serves as a starting point to screen the existing network.
(3) By identifying multimodal expansion or connectivity needs, which helps achieve safer and more connected bicycle and pedestrian networks.
(4) By screening all upcoming resurfacing projects, which allows agencies to incorporate road diets cost-effectively.
Before any road diet can be implemented on a roadway, the City would need to evaluate the impacts on the community, such as traffic diversion to adjacent roadways, travel time changes along the corridor, and costs. Additionally, traffic calming measures should adhere to the City’s NTCP and typically subject to Council approval.
Staff
Written by: Nicole He, Associate Engineer, Public Works
Reviewed by: Carol Shariat, Public Works
Reviewed by: Steve Chan, Transportation Manager, Public Works
Approved by: Michael Liw, Assistant Director/City Engineer, Public Works
ATTACHMENTS
1. Annual Work Plan Topic Request Form-Traffic Calming on Benton Street (Kratz)
2. Annual Work Plan Topic Request Form - Lower Motor Vehicle Speeds and Speed Limits (Kratz)