Traffic Calming Procedures and Process
The Traffic Division shall consider the following actions after receiving notification of speeding from residents of affected streets.
Phase I – Enforcement and Engineering
- Conduct a Speed Survey – The Police Department will work in conjunction with the Public Works Department to conduct a speed survey to determine the extent of the speed or traffic volume and if traffic enforcement can be effectively applied during specific time periods. This will be based on reasonable number of violators exceeding the 85th percentile speed during those identified peak volume time periods.
- Traffic Enforcement – If identified time periods and a reasonable number of vehicles exceed the 85th percentile speed, as determined by the Police Department and/or Public Works Department, then enforcement steps shall be taken. A follow-up speed survey will be conducted if the residents feel that the problem is continuing.
- Establish and Post Appropriate Signage – The Public Works Department may consider the placement of traffic signage and roadway striping if deemed warranted.
Phase II – Traffic Calming Devices
If Phase I steps do not resolve the resident’s complaints, then the Traffic Engineer may consider the following traffic calming devices in the following order. All of these devices would require a 2/3 approval by the residents of the affected street before implementation occurs. The Traffic Engineer may decide to impose any one of the traffic calming devices on an experimental basis prior to moving to Phase III.
- Bot Dots or Painted Lines – The residents must submit a petition requesting either a painted line or bots dots to be placed in conformance with the Caltrans Traffic Manual. The Traffic Engineer shall concur with the selection and authorize the installation.
- Turn restrictions – Directional signage restricting certain turning movements can be considered and installed.
- Painted Chicanes – The residents may request painted curved lines on their street, providing the speed survey shows a continued speeding problem and the Traffic Engineer agrees.
A written ballot provided by the Public Works Department shall poll each affected resident. The Traffic Engineer shall agree to the design and authorize the installation.
Phase III – Physical Road Structures
The following structures will only be considered if Phase II steps did not resolve resident complaints and also require 2/3 approval by the affected residents.
- Chicanes – If the residents and Traffic Engineer feel that the bots dots and/or painted lines have not reduced the speeds (speed survey continues to show a problem), the residents may vote for the raised islands by a mailed ballot from the Public Works Department. Each property owner who would lose a parking space in front of his or her residence must agree in writing. The Public Works Department must approve the raised island design.
- Elongated Speed Humps – The Traffic Engineer may consider the placement of elongated speed humps, provided the criteria set forth in the Speed Hump Policy have been met, and 2/3 of the affected residents have approved through a mail ballot.
Phase IV – Raised Intersections and Street Closures
Because of the seriousness of these two considerations, any approval for recommendation and funding by the Traffic Engineer must be presented to the City Council. These two options also require 2/3 approval by the affected street residents. The City Council may require some or all of the costs to be paid by the residents.
- Raised intersection – The Traffic Engineer may consider the placement of a raised intersection at any residential location when all other options have been taken to reduce speeds and a stop sign or traffic signal is not warranted. A raised intersection is defined as a 12-foot ramp that rises two inches above the roadway surface at a slope of less than 1.4%. Residents on all four corners of the intersection must agree to its placement in writing.
- Street Closure – This would be the final step and would require a traffic study to determine the impact on surrounding streets.
The purpose of a traffic signal is to assign right-of-way to opposing movements of traffic at an intersection. As such, it may be necessary to install a traffic signal if the traffic volume increases and four-way stop signs do not lessen problems. However, improperly placed traffic signals can cause an increase in traffic accidents, particularly rear end collisions and cause pedestrians a false sense of security from crosswalks and red lights, which may result in an increase in pedestrian accidents.
Before installing a traffic signal at an intersection, traffic engineers must evaluate the following questions:
- Does the volume of vehicles entering an intersection create confusion or congestion?
- Is there so much traffic on main streets that it may be dangerous for traffic on side streets to cross? Are accidents the result of this condition?
- Is there an increasing demand for pedestrians to cross main streets?
- Does the number of school children crossing a busy street create confusion, congestion, or hazardous conditions?
- Will the installation of a signal reduce overall congestion?
- Does the accident history indicate that a signal will reduce the number of
accidents at an intersection?
Traffic engineers use national standards to evaluate an intersection that may need a traffic signal. Properly placed traffic signals will decrease accidents and improve traffic flow.
Traffic engineers and technicians are constantly upgrading the signal systems in the City. Traffic flow is being improved on major arterials in Brentwood by coordinating traffic signals, which will allow vehicles to travel along the signalized streets with fewer stops.
Traffic Signals are fully actuated with the following advantages:
- Reduce delay
- Minimize potential for rear-end collisions
- Adapted to handle varying traffic flows
- Battery Back-up to operate from 4 – 6 hours in the event of a power failure.
- Preemption for Police & Fire
- Pedestrian Countdown Signal Modules
If you think there is an intersection that should be studied for a traffic signal; or, if you notice an existing traffic signal that is not operating correctly, please contact the Traffic Engineering Division at (925) 516-5420.
Determining Speed Limits
When a new roadway is constructed or has undergone a significant change in surrounding land use or roadway characteristics, the local agency is required to perform a speed survey in accordance with the California Vehicle Code (CVC) and the California Manual of Traffic Control Devices (MUTCD). A speed survey consists of the speeds, as measured by a radar gun, of 100 vehicles in each direction on any given roadway segment. These measurements must be taken when traffic is flowing freely in fair weather with no unusual conditions present.
The speed limit for any segment of road is set at the nearest 5 mph increment of the 85th percentile speed of the speed survey. The 85th percentile speed is that speed at which 85% of the vehicles are traveling. An 85th percentile speed of 41.5 on a speed survey would establish a speed limit of 40 mph. An 85th percentile speed of 43.8 on a speed survey would establish a speed limit of 45 mph. An additional reduction of 5 mph may be taken if the Traffic Engineer feels it is warranted to meet traffic safety needs of the community.
After the speed limit is adopted by the local agency and appropriate signs installed, the police department can legally enforce the posted speed limits with the use of radar. If no physical changes occur on the roadway the speed survey is considered valid for a period of 7 years, and can be extended up to 10 years if conditions remain constant.
Current Speed Limit Map
Traffic Volume Counts
2007 Traffic Volume Count Map
2005/2006 Traffic Volume Count Map
Average Daily Traffic (ADT) is the number of vehicles traveling past a selected point on a street. ADT’s are counted in a twenty-four hour period with a portable traffic counter.
The portable traffic counter is a totally self-contained unit that monitors traffic flow around the clock to provide data. Utilizing Vehicle Magnetic Imaging Technology, the counter records traffic and vehicle data including:
- Vehicle Count
- Length Classification
- Vehicle Speed
- Roadway Occupancy
The data is then able to exported to software for fast generation of charts, reports and graphs to objectively determine traffic conditions and if modifications are warranted.