|Back To Agenda||Print Page|
SUBJECT: TRAFFIC SIGNAL PRIORITY LIST
Attachment B-TRAFFIC SIGNAL INSTALLATION PRIORITY LIST - PDF
1. Approve a Citywide Traffic Signal Installation Priority List.
2. Direct Staff to present an updated Traffic Signal Priority List to City Council annually.
Due to budgetary constraints and concern for other traffic signal needs Citywide, City Council requested that the Traffic Safety Commission investigate a program to prioritize the need for traffic signal installation and/or modifications on a citywide basis at their September 10, 2005 joint meeting of the City Council and the Traffic Safety Commission.
On June 27, 2005, the Traffic Safety Commission approved the Citywide Traffic Signal Installation Procedure as shown in Attachment A. Based on the approved Citywide Traffic Signal Installation Procedure, 11 locations have been identified as justifying new traffic signal installations within the City. These 11 locations are identified and ranked in Attachment B. On December 12, 2005 the Traffic Safety Commission approved the attached Traffic Signal Priority List.
A Traffic Signal Priority List establishes a hierarchy of needs for the signalization of unsignalized intersections. As previously stated, it will be used as a planning tool to budget for future traffic signal needs on a citywide basis. It allows for future discussions and analysis of requests for signals to take place within the context of citywide needs. Approval of the Signal Priority List is not a recommendation to install a traffic signal at the location with the highest priority. It is a programming and planning tool to aid in the decision-making when and if funding is available and the need for a traffic signal is warranted.
The recommended traffic Signal Installation Procedure for new signal installations involves three phases. The initial screening process to determine if signalization is justified is determined during Phase I (data collection) and Phase II (analysis). For locations where this process has determined that installation of a new traffic signal is justified and appropriate, Phase III applies criteria to rank the eligible locations. The Traffic Signal Installation Procedure is outlined in Attachment A.
Based on this Procedure, 11 locations have been identified as justifying new traffic signal installations within the City. These 11 locations are identified and ranked in Attachment B. The priority list is being submitted for approval and subsequently will be used as a planning tool to help establish funding priorities through the normal budgetary process.
It is important to note that the Traffic Signal Priority List ranks the need for new traffic signal installations at uncontrolled intersections. Priority for existing traffic signals in need of modifications will be assessed on case-by-case basis. Safety is typically the overriding factor that warrants signal modifications. Funding for safety related improvements to existing traffic signals is sought through available grant programs, maintenance budgets or as additions to other budgeted work. These existing traffic signal locations and projects are intended to be included as independent Capital Program Projects and will be budgeted for accordingly. Additionally, Staff is recommending updating, and presenting the updated, Traffic Signal Priority List to Council annually.
Adopting Staff’s recommendations to approve the Traffic Signal Installation Priority List establishes a hierarchy of needs to aid in systematically programming the installation of new traffic signals.
There is no immediate fiscal impact to the recommended actions.
Attachment: A) Traffic Signal Priority Procedure
TRAFFIC SIGNAL PRIORITY PROCEDURE
In Phase I, the following data are collected for any location that has been suggested as a candidate for a traffic signal:
Collisions: A recent three-year compilation of reported collision history differentiating types and correctability is developed.
Traffic Volumes: 24-hour volume counts with an hourly listing of each approach direction are obtained for the combined minor street volumes, the combined major street volumes and a total for the entire intersection. Peak hour (am and pm) traffic volumes by manual count for the turning and through movements are typically obtained.
Pedestrian/Bicycle: As part of the peak hour vehicular movement counts, pedestrian and bicycle data are collected. If the pedestrian and bicycle peak periods differs from the vehicular peak periods, a separate manual count may be taken.
Existing Conditions: The current type of control (two-way stop, all-way stop, etc.) is recorded, along with the posted speed limit, roadway geometry and adjacent developments affecting traffic patterns.
The above data is collected to screen eligible projects, as well as for use in placing justified locations within the prioritization list.
In Phase II, the information from Phase I is combined with further study to determine which locations justify the installation of a traffic signal. An evaluation of traffic conditions utilizing the Caltrans Traffic Signal Warrants provide the first step in evaluating locations for potential signalization. The eight Caltrans traffic signal warrants, as found in the Manual of Uniform Traffic Control Devices (MUTCD) and the MUTCD 2003 California Supplement are complex, with minimum thresholds varying depending upon roadway geometry, approach speeds, type of development, proximity of other traffic controls, etc. The current traffic signal warrant worksheets are attached for reference purposes. A brief description of each warrant is as follows:
Warrant 1 – Eight-Hour Vehicular Volume
This warrant consists of two conditions. Condition A is intended for application at locations where a large volume of intersecting traffic is the principal reason to consider installing a traffic signal. Condition B is intended for application at locations where Condition A is not satisfied and where the traffic volumes on the major street is so heavy that the traffic on the minor intersecting street suffers excessive delay or conflict in entering or crossing the major street. This warrant can also be satisfied if neither A nor B is satisfied, but both A and B are satisfied 80% and adequate trial of other alternatives that could cause less delay and inconvenience to traffic has failed to solve the traffic problems.
Warrant 2 – Four-Hour Vehicular Volume
This warrant is intended for application at locations where the volume of intersecting traffic is the principal reason to consider installing a traffic signal. Since only four hours are considered as opposed to Warrant 1, where eight hours are considered, the threshold volumes are significantly higher than for Warrant 1.
Warrant 3 – Peak Hour
This warrant is intended for use at locations where traffic conditions are such that for a minimum of one hour on an average day, the minor street traffic suffers undue delay when entering or crossing the major street. This warrant is only applied in unusual cases, such as office complexes, manufacturing plants, industrial complexes or high occupancy vehicle facilities that attract or discharge large numbers of vehicles over a short time.
Warrant 4 – Pedestrian Volume
This warrant is intended for application where there is significant pedestrian volume and traffic volume on the major street is so heavy that pedestrians experience excessive delay in crossing. For this warrant to be satisfied, the distance to the nearest traffic signal on the major street must be greater than 300 feet.
Warrant 5 – School Crossing
This warrant is intended for application where the fact that school children cross the major street is the principal reason to consider installing a traffic signal. For this warrant to be satisfied, the distance to the nearest traffic signal on the major street must be greater than 600 feet.
Warrant 6 – Coordinated Signal System
This warrant is intended to maintain proper platooning of vehicles in order to maintain or extend a coordinated signal system. This warrant is not applied when the resultant spacing of traffic signals would be less than 1,000 feet.
Warrant 7 – Crash Experience
This warrant is intended for locations where the severity and frequency of crashes are the principal reasons to consider installing a traffic signal. For this warrant to be satisfied, Condition A or B of Warrant 1 must be satisfied at least 80%, there must be a least five correctable accidents during a 12-month period and adequate trial of less restrictive remedies has failed to reduce accident frequency.
Warrant 8 – Roadway Network
This warrant is intended for locations where it is desirable to encourage concentration and organization of traffic flow on a roadway network. Besides requiring certain volume thresholds to be net, this warrant requires that the intersection consist of major routes.
As mentioned previously, these warrants are merely the minimum threshold levels, which if found to be met, shall result in the analysis of other traffic conditions and factors to determine whether a signal installation or other traffic operational change is justified. As such, the warrants are only part of the engineering study needed to justify the installation of a traffic signal and not the justification or a mandate in and of themselves for installation. In fact, the Caltrans Traffic Signal Warrant Worksheets specifically note the following:
The satisfaction of a warrant is not necessarily justification for a signal. Delay, congestion, confusion or other evidence of the need for right-of-way assignment must be shown.
The Manual of Uniform Traffic Control Devices (MUTCD) also provides guidelines that require evaluation of other traffic conditions beyond just Traffic Signal Warrants:
A traffic control signal should not be installed if it will seriously disrupt progressive traffic flow.
A traffic control signal should not be installed unless and engineering study indicates that installing a traffic control signal will improve the overall safety and/or operation of the intersection.
This further study includes, but is not limited to, the following factors:
1. Analysis of the effect of signalization on existing traffic signal progression systems;
After this comprehensive engineering study is completed, Staff determines whether specific locations justify the installation of a new traffic signal.
For locations where Phase II has determined that installation of a new traffic signal is justified and appropriate, the following criteria are applied to rank the eligible locations (there is no maximum score):
1. Collisions (Max. Points: No Limit)
Points are assigned for each reported collision that occurred at the intersection during the previous three years that was susceptible to correction by signalization, as follows:
Type of Collision Points per Occurrence
The total points for the previous three years are divided by three to determine a yearly average that is then assigned to the proposed signal location.
2. Pedestrians/Bicycles (Max. Points: 30)
A maximum of ten points are assigned for each of the following:
(A) Pedestrians (general)
Points are assigned based on the number of pedestrians crossing the higher volume street during the four highest traffic hours, as presented below:
Pedestrians Points Pedestrians Points
(B) Pedestrians (school)
If the School Warrant (Caltrans Warrant 5) is met, 10 points are assigned.
If the location is identified in the City Bikeway Master Plan, as contained in the Circulation Element of the General Plan, 10 points are assigned.
3. Average Daily Traffic (ADT) Volumes (Max. Points: 10)
Points are assigned based on a comparison of the ADT volumes on the intersecting streets, as presented below:
4. Peak Hour Traffic Volumes (Max. Points: 10)
Points are assigned based on a comparison of side street traffic volume to main street traffic volume during the peak hour, as presented below:
Points are assigned in this category to account for the difficulty that motorists may have judging gaps in traffic on high-speed streets. More points are assigned for the higher-speed streets, as presented below:
Posted Speed Limit Points
6. Special Conditions (Max. Points: 5)
Points are added based on special conditions related to the benefits or drawbacks of signalizing an intersection as determined by the Public Works Department.
Activity Centers (Max. Points: 3)
One point is assigned for each of the following activity centers that generate pedestrian or emergency vehicle traffic and are within 1,000 feet of the candidate traffic signal location:
Other Safety Concerns (Max. Points: 2)
One point is assigned for each of the following safety considerations at the candidate traffic signal location:
- Restricted Sight Distance