Traffic Signal Timing Manual
This publication is an archived publication and replaced with the Signal Timing Manual - Second Edition.
SIGNAL TIMING POLICY
TABLE OF CONTENTS
- 2.1 Policy Development
- 2.1.1 Policy Influence on Signal Timing
- 2.1.2 Challenges to Signal Timing Policy Development
- 2.1.3 Use of Standards
- 2.2 Signal Timing Process
- 2.2.1 Signal Timing Maintenance and Data Management
- 2.2.2 Hardware and Software Considerations
- 2.2.3 Selection of Optimization Tools and Evaluation of Policies
- 2.2.4 Other Policy Considerations
- 2.3 Performance Measures and National Perspective in Signal Timing
- 2.3.1 National Traffic Signal Report Card
- 2.3.2 National Signal Timing Findings
- 2.4 Funding Considerations
- 2.4.1 Direct Signal Timing Funding
- 2.4.2 Partnerships for Funding Signal Timing
- 2.5 Examples of Programs
- 2.6 References
LIST OF FIGURES
- Figure 2-1 Transportation Policy and Signal Timing Application Relationships
- Figure 2-2 Signal Timing Environmen
LIST OF TABLES
- Table 2-1 Signal Timing Strategies, Settings, and Policy Examples
- Table 2-2 Signal Timing Process Examples
2. POLICIES, PROCESS, AND FUNDING
Signal timing is important because it directly affects the quality of our transportation system, which affects virtually everything within our communities. Signal timing impacts the time we spend traveling, the quality of the air we breathe, the safety of roadway travel, the costs of our trips, and many aspects of our daily lives. Signal timing policy is important because it is a way to help control and define priorities within the transportation system and how signal timing is applied. A clearly defined signal timing policy should be an extension of a region’s transportation policy reflecting a region’s values in the operations and safety of their transportation network. The context of the term policy is to support strategic objectives, and do not represent global applications in most cases. Engineering judgment should be used in concert with policy development and applications in the signal timing realm.
This chapter describes the relationship between transportation policies and signal timing applications, summarized in Figure 2-1.
Figure 2-1 Transportation Policy and Signal Timing Application Relationships
This chapter contains five sections.
- The first section presents a summary of policy development.
- The second section provides an overview of the signal timing process and considers how policies should affect several decisions made during signal timing. Examples of different signal timing policies are provided as well.
- The third section presents performance measures and a national perspective with regards to signal timing.
- The fourth section presents a discussion of various funding considerations for signal timing.
- The final section presents examples of programs that have been effective in coordinating signal timing, policy, and performance measures.
2.1 POLICY DEVELOPMENT
The diagram at right illustrates the policy development cycle discussed in this section. Signal timing policies flow from the overall regional transportation objectives. Local considerations are taken into account prior to initiating the specific timing process. Operation of the system generates user feedback that, in turn, drives overall policy.
Regional transportation policies, and more specifically signal timing policies, guide the strategy for how to operate signalized intersections, devices, signal timing equipment, and for prioritizing travel modes and/or transportation facilities at a system level branching beyond jurisdictional boundaries. Regional transportation policies should be used to help establish signal timing policies, providing guidance in the development of specific objectives for the implementation of signal timing plans. The development of local signal timing strategies should consider the regional transportation policies to determine if there are regional objectives that will influence the process. These policies may also be consulted to determine their effect on ongoing operations and maintenance activities. The regional transportation policies are a result of a community visioning process that develops a plan that:
- sets the direction and guides the planning for improvements for a region's transportation system during the next 20 years;
- establishes policies and priorities for all forms of travel – motor vehicle, transit, pedestrian, bicycle and freight – and street design and the efficient management of the overall system;
- anticipates the region's current and future travel needs based on forecasts of growth in population, households and jobs as well as future travel patterns and analysis of travel conditions;
- evaluates federal, state and local funding that will be available for transportation improvements; and
- estimates costs of projects and proposes funding strategies to meet these costs.(1)
The plan is typically developed with the help of elected leadership and ultimately represents the attributes the community hopes to address. Examples of this type of plan include a Transportation Improvement Program (TIP), a Capital Improvement Program (CIP), a Long-Range Transportation Plan (LRTP) and others.
The signal timing policies should establish the signal timing objectives and performance measures for a jurisdiction all the way down to a particular facility or intersection.
Location-specific considerations must also be identified to determine whether a specific corridor or area has special needs. For instance, a city may have a policy of maintaining a high level of mobility on its arterial street system, but that may not be applicable within a downtown area that may have a policy of maintaining access. An important step in the flow chart to the right is to consider the special needs before moving to the next step of the flowchart.
The signal timing policies can be used to refine the scope of what is to be accomplished during the signal timing process. Signal timing policies should establish answers to the following questions:
- What should be improved?
- What objectives or various user needs should be optimized?
- What performance measures should be tested?
- What standards must our policy follow?
- What data should be collected to develop signal timing?
- What should be measured after implementation?
- What should be monitored as part of maintenance?
Agencies should use their signal timing policies to guide the development, operation, and maintenance of their signal system.
2.1.1 Policy Influence on Signal Timing
The primary goal of traffic signal timing is to maintain the safe and efficient transfer of right-of-way between conflicting streams of users; however, a safe and efficient system varies within each community’s context as described previously. Thus, local, regional, state, and federal policies must be considered to determine a proper approach. These policies form the foundation from which performance measures are selected. These performance measures should be tracked through the signal timing process.
Policy questions related to signal timing include determining:
- Whether all types of users (transit, freight, emergency respondents, pedestrians, vehicles, bicycles, etc.) will be treated equally or prioritized at the signalized intersection;
- How frequently will signal timing plans be reviewed and updated;
- How approaches with differing street classifications should be treated;
- Whether there will be preferential treatment for certain movements beyond the definition of the coordinated phase (will the coordination timing plan clear all queues during each cycle for left turns and side street through movements);
- How intersections with deficient capacity will be treated; and
- What measures will be used to determine whether the timing plan is effective (vehicle stops, network delay, arterial travel speed, estimated person delay, estimated fuel consumption, transit speed, etc.) and how will they be collected.
Signal timing by its nature is the assignment of right-of-way to competing directions and travel modes. Signal timing often requires trade-offs between various modes at an intersection, such as vehicles versus pedestrians and bicycles. These tradeoffs could result in competing ideas, such as safe pedestrian crossing times versus maximizing automobile capacity.
For every action, there are following reactions, and these types of trade-offs with signal timing should be made clear in the mind of decisionmakers in order to ensure signal timing policy is developed within the correct context. Examples of these trade-offs can be seen in the following portion of this section.
Policies help define the objectives for signal timing plans. User expectations for a street network are often the guiding principles for an agency’s policies. There are many types of users, including rail, pedestrian, bicyclists, transit, emergency vehicles, and automobiles; however, it is the prioritization of these users on a facility that should reflect an understanding of agency policy and, in turn, provide signal timing objectives. Traditionally, rail is given the highest priority due to its greater momentum and limited braking characteristics relative to other modes of travel. This is seen when there is a rail crossing and all movements are preempted in deference to the rail movement when a train is approaching. Other priority considerations include preemption or priority service for emergency vehicles (preemption overrides normal phasing sequence and coordination; priority service does not). An agency can provide emergency vehicles with devices that give them preference (preemption or priority) when needed. An agency can provide signal priority to transit vehicles to facilitate higher mobility (a bus can transport more people than an automobile) while being less disruptive to other system users. Details regarding signal preemption, priority, and other advanced signal timing topics are covered in Chapter 9.
Each of the signal timing policies and expectations may vary based on the users, roadway facilities, and mode split. For example, the user expectations and objectives for a downtown core are different from those in a suburban setting. Within the Central Business District (CBD) of a medium or large city there are many users to consider. There are typically a higher percentage of pedestrians and transit vehicles in this setting and, as a result, the signal timing should reflect those users. Outside the CBD, the focus may change to one of maximizing mobility for various users. On a major arterial, for example, the focus may be on a policy of decreasing travel times, number of stops, and delays for users on the major street while accommodating transit and emergency vehicles.
CBD environments require substantially different timing strategies than high-speed arterials. No single policy is correct for all situations. Each policy is site-specific and based on agency policy. It is often difficult to have a policy that completely satisfies all interested parties, as some policies inherently shift priorities from one user group to another. Regardless, the traffic engineer should ensure that the measures of effectiveness used to evaluate a system’s performance are appropriate for the policy being implemented. In addition, the traffic engineer is often best served by using a tool which can analyze the desired measures of effectiveness for optimization and evaluation. A signal timing tool that only optimizes for vehicles may need to be adjusted to the unique requirements of transit which are not reflected in many traditional signal optimization packages.
Current local and state agency signal timing policy ranges from very well-defined and well-implemented to non-existent. Based on a review of state and local agency signal timing policies, Table 2-1 shows some generalized signal timing strategies and examples of applicable signal timing policies that would apply on a case by case basis.
Signal Timing Strategy
Downtowns, Schools, Universities, Dense Multi-Use Development, Parks, or any location with high pedestrian/bicycle traffic.
Shorter cycle lengths to reduce wait times
Extended Pedestrian crossing timing
Exclusive Pedestrian Phasing
Leading Pedestrian Interval
Transit-corridors, along transit routes, near transit stations or crossings.
Signal preemption for high importance transit modes (i.e. rail)
Signal priority for strategic transit modes and routes
Signal coordination based on transit vehicle speeds
Extended Pedestrian crossing timing
Exclusive Pedestrian Phasing
Leading Pedestrian Interval
Key roadways and routes to and from hospitals, fire stations, and police stations.
Signal preemption for high importance vehicles
Automobile-Focused / Freight-Focused
Locations with high automobile or truck/freight traffic, facilities of regional importance, freight corridors, ports, or intermodal sites.
Avoid cycle failure (i.e. queued vehicles not making it through the intersection on a single green indication)
Maintain progression on coordinated systems as best as possible to avoid unnecessary stops and delay
Use appropriate cycle lengths (Shorter cycle lengths will typically result in less delay, but increased “lost time” (time lost in vehicle deceleration, driver reaction time, and vehicle acceleration), while longer cycle lengths may result in more delay, less “lost time”, and potentially more vehicle throughput depending on traffic demand)
Ensure appropriate pedestrian signal timing to allow safe multimodal use of the roadway network.
Low-Volume Locations or Periods
Locations with low traffic volumes or during off-peak travel periods
Ensure efficient signal timing operations (avoid unnecessary stops and delays)
Consider flashing operation (yellow-red or red-red) if conditions allow
Use appropriate resting state for the signal with no traffic demand (i.e. rest in red, rest in green and “walk” on major roadway)
Allow skipping of unnecessary movements (i.e. uncalled left-turn phases) but assure it does not create “yellow trap”
Use half, third, or quarter cycle lengths relative to other coordinated signalized intersections
Allowing pedestrian actuations to temporarily lengthen a cycle length, removing an intersection out of coordination, if pedestrian and vehicular volumes are low.
Each of these generalized signal timing policies reflects the priorities in a transportation system. These priorities should match the regional characteristics of travel in an area, as well as the roadway classification.
2.1.2 Challenges to Signal Timing Policy Development
There are distinct challenges associated with interpreting policies and implementing them within traffic signal timing settings. Policies often provide agencies and individuals with considerable room for interpretation. In many cases, an agency’s established policies are not fully understood by the implementing staff, or the implementing staff may not recognize that policy is being established. This is further complicated by the public’s lack of understanding of the signal timing complexities. Implemented signal timing settings that are consistent with the policies (either explicitly or by default) may be changed due to public response or complaint and the resultant changes may not be consistent with policy. A further challenge for the practitioner is that the policymaker may not appreciate the technical complexity and financial implications associated with the actual implementation of the strategy created to address a specific policy. For this reason, it is important to emphasize the relationship between transportation or signal timing policies to performance measures and funding. Details on both are presented later in this chapter.
Many agencies do not have written policies, and there is a poor understanding of the relationship between the settings used in the field and their effects on operations. Historically, many traffic engineers have made decisions based on user expectations and complaints, which may not represent best practice or the agency’s policy. For example, an agency’s operations standard may dictate the minimum level of service (LOS) of a signalized intersection, which, in turn, determines the capacity and the size of the intersection to achieve this LOS. This policy may result in long pedestrian crossing times, yellows, and all-reds, which can increase the cycle length for the intersection (assuming that pedestrians are present and will try to cross the wide street). The long cycle lengths increase the delay for pedestrians, which may reduce the compliance of pedestrians or increase mid-block crossings (to avoid the signal).
Similar to best design practices, a context sensitive approach can be applied and can benefit signal timing. A context sensitive approach considers the environment of the traffic signal, the local policies, and the unintended consequences of potential changes as a result of the signal timing changes.
Signal timing is also complicated because operators have no clear way to measure the ongoing operations of the entire traffic signal system. Traffic signal operation is an area that is more complicated than freeway operations, and it is difficult to identify effects of changes to the systems without the infrastructure to measure performance. Research related to arterial performance measurement is underway but has been limited in its application. An example of this is freeway management system maps that produce real-time speeds for traveler information. Recent research (NCHRP 3-79) identified that one challenge to producing similar maps for the arterial system is the complexity of measuring performance at each intersection. An additional challenge is the lack of infrastructure to communicate the information back to a location where it can be displayed.
Despite these challenges, the development of signal timing policies that follow regional and local community transportation goals and objectives is a worthwhile undertaking.
Development of signal timing policies should be a collaborative effort between regional partners and community stakeholders, crossing jurisdictional boundaries, with the service and safety of the customer in mind at all times. Signal timing policies should be clearly documented and thoroughly communicated within an agency to those who operate and maintain the signal system.
2.1.3 Use of Standards
Within all signal timing policies, there should be implicit or explicit direction to use the latest national and local standards available relating to signal timing and operations along with good engineering judgement. Specific standards applying to signal timing can be found in the Manual on Uniform Traffic Control Devices (MUTCD) as adopted by a given state, or other local adopted standards which may follow the uniform vehicle code model.
Standards specific to signal timing in the MUTCD relate to establishing safe and consistent pedestrian crossing times, vehicle clearance intervals, and signal indications, but don’t specifically standardize timing parameters. The MUTCD does provide guidance and options for timing parameters of walk, flashing don’t walk, solid don’t walk, yellow, and all-red indications, which in name are not standards, but many states have interpreted guidance statements as having the force and effect of a standard, thus being mandatory. Still all standards, recommended practices, guidelines, and options should be applied with good engineering judgment. Public safety regarding signal timing and signal timing policy should be of the utmost importance.
A state supplement to the MUTCD may be relevant to provide boundary conditions for the signal timing. Many states produce Manuals of Traffic Signal Design, which may also identify guidance for signal timing settings.
A state’s Vehicle Code can also affect vehicle clearance interval timing. A good example of this is laws related to change intervals which vary depending on whether a restrictive or permissive yellow law is in place. Details on how this affects yellow clearance timing can be found in Chapter 5.
It is important to note that this document is not intended to take precedence over federal, state, or local policies. The Signal Timing Manual provides a comprehensive compilation of materials that should be considered when developing timing plans.
2.2 SIGNAL TIMING PROCESS
The signal timing environment has two components, the signal timing policy and the signal timing process. The signal timing policy should define how and with what form the signal timing process is implemented, and thus should actually include the signal timing process. As described in the previous section, signal timing policies should be used to refine the signal timing process.
Figure 2-2 Signal Timing Environment
The process for developing a signal timing process is often well established in many agencies and focused on the mechanics of optimization. In many cases, the process may be affected by the time, funding, or resources available. Signal timing is a process that uses distinct procedures and one interrelated procedure. Data management, signal timing optimization, field deployment, and performance evaluation are the four quadrant procedures described in the FHWA report on Signal Timing Process, but to think beyond the specific activities we have added additional steps to focus the engineer or technician on other concepts that need to be considered. This expanded signal timing environment, shown graphically in Figure 2-2, provides a framework to achieve results consistent with overall regional and agency policies. As shown in the figure, once the policies have been established, a signal timing process can be implemented, which is further described in Chapter 7.
It is important to consider the context and variations within which the signal timing process can be applied, and the level to which specific policy plays. The signal timing process can occur at a basic, isolated intersection timing level or it can occur at a larger, area-wide or corridor-wide scale involving signal timing, a review of signal hardware and software, signal communication technology and a myriad of other signal system applications. The level and detail of policy confirmation/evaluation on a signal timing project is likely to be greater as the scope, size, or importance of the project increases. Table 2-2 shows examples of the difference between signal timing processes focused on a single intersection and a focus on regional signal timing.
Signal Timing Process Steps
Single Intersection Field Adjustment
Regional Signal Timing Optimization
Typical maintenance is performed on a routine basis
A detailed scope of work is developed and the effort is completed every one to five years
Phone call complaints may be the only step necessary, but could include other sources of data
Turning movement counts, existing signal timing sheets, “before” travel time runs, signal timing policy, etc…
Build signal timing model, typically using a software tool like Synchro or TRANSYT-7F.
Implement New Timing Plans
Change setting and observe
Code signal controller with new timing plans and implement in the field
Fine Tuning / Refinement
Observe and call back person(s) who complained for feedback
Observe and adjust/refine timing plans in the field
Evaluation / Performance Measurement
Customer satisfaction; more complaints?
Conduct “after” travel time and/or delay studies in the field. Compare measures of effectiveness in signal timing software such as Synchro.
Policy Confirmation/ Evaluation
Compare signal timing and traffic operations in the field to prescribed policy.
Make change in timing in the office
Develop documentation of adjustments and results of signal timing effort.
Signal timing optimization at all levels, should ideally begin with a review of established policies to ensure compliance and consistency of the project scope with agency policy. As described in Table 2-2 above, response to routine complaints and maintenance activity may not result in activity in each step of the process, but it is important to start with a framework that could be used during a comprehensive evaluation. Ultimately, consideration of policies must also be relevant to the specific requirements and location of each situation to consider a proper timing plan.
2.2.1 Signal Timing Maintenance and Data Management
The monitoring of signal timing operations and maintenance is included as the last step of the signal timing environment and can take place in a variety of ways. Proactive examples would be a signal timing policy for regular timing updates, field inspections, continual maintenance of signal systems, and communications to to identify issues as soon as possible. Reactive examples would be responding to phone calls from the public or notification from outside sources. Where possible, a proactive approach to monitoring, maintenance, and the entire signal timing process is preferred.
A proactive approach will provide the opportunity for reliable and efficient signal timing and systems operations, particularly in capacity-constrained corridors or regions. The importance of proactive maintenance, monitoring and updates should be made clear in the minds of decisionmakers.
An important part of the maintenance of signal timing plans and the signal system is good, clear data management. Efficiency and cost-savings will be lost if there is not good documentation or recordkeeping of the process so that it can be recreated and/or followed when future signal timing efforts are needed or when a timing setting is called into question in court proceedings. Organized and simple data management is needed to organize the collected data, track changes in the controller, cabinet or other signal infrastructure, record maintenance efforts and implementations, etc. Ideally data management should be redundant in nature to avoid the loss of data in the future. This may take the form of hard copy notes or data in files or binders, as well as electronic copies stored via computer. A little effort to organize data and efforts related to the signal timing process will have large benefits in the future.
2.2.2 Hardware and Software Considerations
While the policy evaluation is undertaken, it is also important to complete an assessment of the hardware and software signal system capabilities and constraints. This effort will provide the agency with an understanding of how certain hardware and/or software capabilities and constraints might enhance or limit their ability to carry out a certain policy. For example, if transit vehicles are a priority in a system or corridor, transit signal priority may be a desired element within a signal timing policy. Yet transit signal priority is a relatively new technique that may require a jurisdiction(s) to upgrade their hardware and software signal controller capabilities to be able to operate transit signal priority and allow this policy to be carried out. Within the evaluation of signal timing policies, the agency needs to consider the tools and resources necessary to collect and evaluate relevant data for optimization and necessary to complete a policy evaluation.
The age of signal equipment is typically related to hardware and software capabilities and constraints. As improved technology is introduced into the transportation industry, signal equipment capabilities increase, and constraints such as lack of memory to store timing plans and other problems decrease. In most cases, traffic controllers purchased today are contemporary electronics with central processors that provide sufficient capabilities for the operation of most strategies that can be developed. The Advanced Transportation Controller (ATC) standard (http://www.ite.org/standards/atc/) provides a hardware platform that anyone can provide software and thus affords opportunities to select from multiple vendors both hardware and software, allowing more upgrade opportunities without changing the hardware. In addition to the signal controller, the hardware at the intersection, the detection, and communication are important factors in the ability to effectively implement the policies described above. Examples of hardware and software constraints include:
- Maximum number of signal timing plans (e.g. an older controller may only be able to store and operate 5 timing plans, while newer controllers can store and operate 20 plans or more);
- How pedestrian crossing requirements will be accommodated in selecting the cycle length (with the primary risk being loss of coordination);
- How planned transitions to and from coordination (e.g., preemptions, plan changes) will be handled;
- How different types of users will be detected and accommodated;
- Capability to implement preferential treatment (preemption or priority);
- Ability of equipment to accommodate regional or corridor communication strategies (i.e. fiber, modem, radio, etc); and
- The hardware and software uses of neighboring agencies and the partnership possibilities between them (i.e. cost-sharing). 2-10
2.2.3 Selection of Optimization Tools and Evaluation of Policies
The data collected as a part of the signal timing process is entered into an optimization tool to evaluate the adjusted signal timing plan. Part of the evaluation should include a confirmation that signal timing policies are upheld by the new timing plans. There are a number of computer programs that can be used to generate signal timing plans. The FHWA recently published a report that describes the resources available in more detail (Traffic Analysis Toolbox, https://ops.fhwa.dot.gov/trafficanalysistools/toolbox.htm). The pertinent questions related to the process for optimization and use of the policy evaluation tool include:
- Is the optimization tool capable of providing an interface that resembles the hardware and software and can it reasonably replicate the performance of the equipment?
- Is the optimization tool capable of producing a plan that addresses the measures established within the evaluation criteria?
- Is there an evaluation tool (other than the optimization tool, potentially simulation) needed to assess whether the timing plan has met the relevant policies?
2.2.4 Other Policy Considerations
Additional policy issues that are more detail oriented include:
- The maximum allowable cycle length;
- Whether the agency will allow lagging and leading left turns by intersection or variable by time of day;
- Whether the agency will allow the skipping of left turn phases under low volume conditions;
- Whether maximum green times will operate within the coordination plan;
- Whether transit preferential policies such as transit signal priority will be implemented aggressively;
- The number of signal timing plans (time of day plans) in operation per day to respond to fluctuating traffic demand;
- Will coordination timing plans allow intersections to temporarily leave coordination to accomplish tasks (i.e. serve pedestrian calls); and
- Whether coordination patterns will be selected by time-of-day or by real-time traffic data.
Hardware and software options are becoming more complex relative to implementation of coordination plans, and it is important to understand that there are differences between signal timing plans produced by optimization tools in the office and the plans that are actually implemented in the traffic signal controller specific to a jurisdiction. In some cases, signal controller software requires a timing plan to provide sufficient time for pedestrians to cross the street for a coordination plan to take effect. While software programs have greatly reduced the effort required to install the controller parameters there is still a significant difference between field operations and the optimization packages. Some signal system vendors are integrating the ability to transfer signal timing and traffic volume data into optimization tools into their products. This further reduces the barrier between data collection, optimization, and implementation; however, this may come at the expense of an assessment of the timing policies and the flexibility of establishing the proper evaluation criteria. This integration might also limit the user to the particular program integrated into the product.
2.3 PERFORMANCE MEASURES AND NATIONAL PERSPECTIVE IN SIGNAL TIMING
Performance measures are the best way to gauge the effectiveness of signal timing policy and its application. Common performance measures related to signal timing include delay per person or vehicle, travel time, 50th-percentile and 95th-percentile queue lengths, and air quality or vehicle emissions measures. Presenting performance measures in a clear and understandable format is important to capturing the attention of policy-makers and decision-makers and reinforcing the importance of good signal timing application within their community(s). Specifics on performance measures are presented in Chapter 3.
2.3.1 National Traffic Signal Report Card
The exposure of signal timing practice has greatly increased at the local, state, and federal levels after the release of the first National Traffic Signal Report card was first released by the National Transportation Operations Coalition (NTOC) in April 2005 and most recently in October 2007. The report card was an agency self-assessment based on the five core areas for agencies and decision makers to focus on when striving for excellence in traffic signal management:
- Program Management – having “clearly defined goals with measureable objectives and specific milestones for achievement to hopefully resulting in improved operational performance, reliability, asset duration, and resource allocation.”
- Traffic Monitoring and Data Collection – often underestimated in importance, “having specific, clear knowledge of conditions allows transportation professionals to be creative in signal timing solutions, by minimizing unknown variability.”
- Routine Signal Timing Updates – “to keep pace with changing travel patterns, traffic signal timing should be actively monitored, reviewed, and updated at least every three years and possibly sooner depending on growth and changes in traffic patterns.”
- Sound Maintenance Practices – “well-trained technicians are needed to properly maintain traffic signals and preserve the investment in hardware and timing updates.”
- Appropriate Traffic Signal Hardware – “to keep from using outdated equipment to operate the signal system, signal controllers (and potentially signal communication network) should be upgraded every 10 years, and possibly more frequently in high-growth areas that require more complex control.”
The report card studies site numerous benefits in the form of reduced congestion, less vehicle emissions, and improved operational safety. These policies listed above are fairly universal best practice policy elements for urban and suburban environments, and many are applicable in rural environments. Establishing improved signal timing policies should lead to improved signal timing and signal operations resulting in improved report card grades.
The NTOC 2005 and 2007 National Traffic Signal Report Card concluded that many agencies do not have documented policies on how signals are operated, nor is this information shared with employees. In addition, regular meetings with law enforcement and emergency service providers, and annual reviews of major roadways are rarely conducted (2). The report card indicated a strong need for improvement in all five categories on average for the 417 responding agencies, with an overall national grade of “D“ in the latest report card, up from a “D-“ national average in 2005.
While the NTOC 2007 National Traffic Signal Report Card showed room for improvement nationally, a few agencies showed significant improvement. This improvement in general was characterized by (1) more effective management techniques, (2) a more thoughtful approach to resource allocation, (3) new or improved training for staff, and (4) improved communication between neighboring agencies and internal departments (i.e. engineering, technicians, and law enforcement), among others.
Many of the improved agencies noted the 2005 National Traffic Signal Report Card provided them validation and numbers to back up requests for additional funding and resources for signal timing projects.
“The agencies managing our traffic signal systems can and want to do better in the daily management of our systems, but this will be accomplished only through the support of local public sector leadership. Proactive traffic signal management, operation and maintenance are critical – our quality of life and the environment depend on it.” – 2007 NTOC National Traffic Signal Report Card
2.3.2 National Signal Timing Findings
Good signal timing will contribute to the safe and efficient movement of goods and persons, not just automobiles, through a region’s transportation system. Unlike other transportation improvements, improved signal timing typically requires little or no infrastructure costs and produces a very high benefit to cost ratio by operating the existing system with greater efficiency and reduced congestion. The cost to retime and optimize a signalized intersection is approximately $2,500 to $3,100 per signal per update (3). Beyond signal timing optimization, establishing or improving signal coordination or updating signal software and hardware equipment can add further system benefit to the traveling public.
The following are some specific examples of signal timing optimization and signal system improvement benefits experienced in various communities nationwide, as documented in the United States Department of Transportation’s Intelligent Transportation Systems for Traffic Signal Control, Deployment Benefits and Lessons Learned (3):
- The Traffic Light Synchronization program in Texas demonstrated a benefit-cost ratio of 62:1, with reductions of 24.6 percent in delay, 9.1 percent in fuel consumption, and 14.2 percent in stops.
- The Fuel Efficient Traffic Signal Management program in California demonstrated a benefit-cost ratio of 17:1, with reductions of 14 percent in delay, 8 percent in fuel consumption, 13 percent in stops, and 8 percent in travel time.
- Improvements to an eleven-intersection arterial in Saint Augustine, Florida, showed reductions of 36 percent in arterial delay, 49 percent in arterial stops, and 10 percent in travel time, resulting in an annual fuel savings of 26,000 gallons and a cost savings of $1.1 million.
- A project in Syracuse, New York, that connected intersections to a communications network produced reductions in travel time of up to 34 percent. Coordinated signal systems improve operational efficiency and can simplify the signal timing process.
- In areas of rapidly changing or unpredictable traffic volumes, adaptive signal timing control may improve system performance by 5 to 30 percent, but should be applied with caution to intersections or corridors.
- Spending less than 1 percent of the total expenditure on highway transportation would lead to a level of excellence in traffic signal operations. It would be an investment with a 40:1 benefit-cost ratio and would result in benefits of as much as $45 billion per year. This corresponds to a price of less than $3 per U.S. household resulting in savings of $100 per household per year. (2, 16)
These national signal timing statistics are meant to show a glimpse of the potential signal timing optimization benefits that can result from either implicit or explicit signal timing policy applications. Communicating these types of benefits to policy-makers and decision-makers is likely one of the best ways to bring attention and funding to signal timing and ultimately, the development of solid signal timing policies.
2.4 FUNDING CONSIDERATIONS
This section discusses the various funding considerations and sources for a signal timing program. Potential funding sources can include federal funding, state-local arrangements, public-private partnerships, and direct agency funding sources.
2.4.1 Direct Signal Timing Funding
Direct agency funding has been the most common approach to funding improved signal timing plan development and plan implementation. Depending on the local, state, or federal level of agency, direct funding sources may include (4):
- General Tax Fund (i.e. gas tax, license tax, property tax, sales tax);
- Bond Proceeds/Interest Income;
- Federal Aid (i.e. CMAQ, Surface Transportation Program, SAFETEA-LU), and
- Developer Mitigation Funds or Impact Fees.
Funding for signal timing projects is available through federal or other sources. For federal funds, the project sponsor must communicate the need for the project with either the State department of transportation or local metropolitan planning organization to determine whether the program fits into the local long-range transporation plan and whether the current transportation improvement program can be amended, if necessary, to include the project. If not, the project sponsor must work with the local or state representatives to make sure the project makes it into the next transportation improvement program update cycle. The planning partners' responsibility is to help qualifying projects obtain funding from either federal or other sources (3).
Federal funds through the FWHA Surface Transportation Program and CMAQ can be used for project, operations, and maintenance costs of a traffic control system and are eligible for Federal reimbursement through the Federal Aid Program. This aid is distributed to project sponsors in the following ways (3):
- Transportation Improvement Program (TIP) and State Transportation Improvement Program (STIP). Program funds are typically available for capital improvement projects requiring new or reconstructed infrastructure. The installation of traffic signal systems and traffic control centers will usually be funded under these programs. These funds are programmed into the State's Long Range Transportation Plan (LRTP).
- Congestion Mitigation and Air Quality (CMAQ) Improvement Program funds. For projects located in air quality non-attainment and maintenance areas, CMAQ funds may be used for operating costs for a 3-year period as long as those systems measurably demonstrate reductions in air quality emissions or increased air quality benefits. Typical eligible operating costs include labor costs, administrative costs, costs of utilities and rent, and other costs associated with the continuous operation of the system, such as costs for system maintenance.
2.4.2 Partnerships for Funding Signal Timing
Beyond a single agency funding source, partnerships play a key role in maximizing the benefits of signal timing projects and fund sharing between agencies. In some cases, public-private entities may offer investments to be used more efficiently and effectively. Good examples of this partnering for funding include Oakland County, Michigan’s Signal Retiming & Maintenance Agreements (5, 6) and the City of Portland, Oregon’s partnership with the Climate Trust (7).
In 2002, the Road Commission for Oakland County, Michigan, began a program to retime nearly 900 signals, in three manageable phases. These phases crossed jurisdictional and public-private boundaries, allowing for the best possible signal timing for the roadway network as a system. Partnerships in this Oakland County effort were formed between the Michigan Department of Transportation (MDOT); the Southeast Michigan Council of Governments (SEMCOG); Wayne County; the Road Commission of Macomb County; the cities of Ferndale, Pontiac, and Royal Oak; and regional consulting engineers. Notable reductions in delay, emissions, and improved travel times were the greatest user benefits measured through this signal timing and implementation partnership, which benefits all agencies involved. Funding for this signal timing effort came through a cost-sharing effort between MDOT CMAQ funds (1/3 of costs) and SEMCOG CMAQ funds (2/3 of costs).
The City of Portland, Oregon’s funding partnership with the Climate Trust is another example of partnering with multiple agencies to achieve a mutually beneficial goal of retiming 170 metro-area traffic signals. The partnership included the Climate Trust, a non-profit organization to support climate change solutions to offset greenhouse gases, because of their vested interest in the environmental improvements associated with good signal timing; the various agency partners (City of Portland, Washington County, and the Oregon Department of Transportation) have a vested interest in improving the efficiency of their roadway systems through signal retiming. A shortfall of available public funds to support signal retiming and implementation led to a partnership with the Climate Trust to make use of their available carbon dioxide offset funding in this signal retiming effort.
According to the Chicago Area Transportation Study website (8), their CMAQ program finances three types of traffic flow improvements—bottleneck elimination, intersection improvements, and signal interconnection—that all impact signal timing plans, but do not directly fund signal timing plan development. Signal timing improvements could qualify as “other projects” for CMAQ funding because improved signal timing reduces stops and idling traffic in a network, which results in emission reductions that could be estimated.
A unique signal timing partnership offer is available in the San Francisco Bay Area through the Metropolitan Transportation Commission’s (MTC) Regional Signal Timing Program. This program invites local cities and counties to apply for “assistance from MTC's consultants for development and implementation of new time-of-day traffic signal coordination plans for weekday peak periods. The budget is $1.5 million in federal funds, with which about 650 traffic signals may be retimed. MTC will provide the local matching funds. In previous cycles, all applications that met eligibility requirements were funded. Other public agencies, such as congestion management agencies or transit agencies, are also eligible to apply if authorized to act on behalf of the agencies that operate traffic signals within the project limits (9).”
Places to start for securing funding for signal timing projects could be through a local MPO planning office. Traffic signal retiming projects might be added to their Long Range Transportation Plan (LRTP) as well as their more immediate Transportation Improvement program (TIP). For locations outside of MPO areas you can check with your local state DOT office to possibly add this work to their transportation plan.. For more information on federal level funding, contact the State FHWA Division Office. Reaching out to regional partners, as shown in the examples above, can be a great step towards securing funding for signal timing projects that can be mutually beneficial (3).
2.5 EXAMPLES OF PROGRAMS
The following section provides several examples of various signal timing policy applications corresponding to the array of modal objectives.
City of Denver, Colorado. The fundamental part of the Traffic Signal System Improvement Program (TSSIP) is development of new signal timing plans at a regional level in a three- to five-year cycle for major corridors and for all capital projects implemented (including miscellaneous signal equipment purchases). Since 1994, across 14 operating agencies in the region, the programming of TSSIP projects has been completed with regional cooperation and consideration for equitable distribution of resources from federal, state, and regional entities. Because the TSSIP is funded with federal Congestion Mitigation Air Quality funds, the benefits of every project must be measured and reported. The workgroup also targeted some additional funds for selectively developing timing plans that address weekend traffic patterns. Specific criteria would be developed to guide the selection of which weekend timing plans the TSSIP would prepare. Development and evaluation of timing plans for traffic-responsive control and incident management test bed activities are also included in this activity, as is assessment of the transit signal priority projects. (15)
City of Philadelphia, Pennsylvania. The City currently has informal agreements with two neighboring townships, Upper Darby and Springfield, to provide arterial signal coordination across jurisdictional boundaries, which results in improved operations for all users. (14)
City of Portland, Oregon. The City of Portland incorporates many travel modes within their signal systems. The expectations vary based on the surrounding areas and type of users. Within the downtown core, mobility for pedestrians, buses, bicycle, and train modes are the main focus. The coordinated system allows the transit modes to travel with higher priority than automobiles. The signals are timed to keep travel speeds relatively low. The low speeds and short cycle lengths allow a safer environment for pedestrians. Outside of the downtown core area, the coordinated system changes the focus to allow higher mobility for autos while still accommodating transit, emergency vehicles, bicycle, and pedestrian users. Transit signal priority is implemented along a majority of bus routes and emergency pre-emption is installed at all signalized intersections. Bicyclists are often provided with bike lanes in the streets and at some locations a bicycle signal is installed to provide them with additional mobility. Pedestrians are also considered within the signal system with pedestrian recall parameters. The networks set the coordination reference point at the beginning of the “Flashing Don’t Walk” time to ensure sufficient pedestrian service on the coordinated phases and to provide a “rest in Walk” operation that benefits pedestrians. In addition, an exclusive pedestrian phase is provided at high pedestrian areas.
City of San Francisco, California. The Bicycle Advisory Committee in San Francisco, California, has brought forth several unique signal timing policy suggestions to aid bicyclists. Because effective signal timing can improve traffic flows and reduce stops and delay, for bicycles, the Bicycle Advisory Committee recommends that the City consider “timing the signals along bike routes for bicycle speeds of approximately 12 to 15 miles per hour.” In addition, minimum green times and red clearance intervals should take the bicyclist into consideration because bicyclists need more start-up time to get through an intersection. They are recommending that the City actuate signal timing to include “at least 8 seconds” of minimum green time and more if the grade is uphill. Along major thoroughfares, particularly with widths greater than 75 feet, they say “red clearance intervals should be provided to allow time for the bicyclist to clear the intersection before cross-traffic is given a green indication.” (11, 12, 13)
City of Vancouver, British Columbia. The Vancouver Transportation Plan contains a number of policies that are intended to improve the comfort and convenience of pedestrians in the City. One proposed measure is to reduce pedestrian wait times at traffic signals. Requests to reduce pedestrian wait times at signals were received during the public consultation phase of the Transportation Plan. The Transportation Plan recommended this reduction. The issue is also emerging through City Plan Community Visions. A related issue is that pedestrians (or cyclists) are more likely to ignore the signal if wait times are perceived as too long. This can cause pedestrians to cross against the light and result in a signal changing with no pedestrians (or cyclists) crossing. This also affects transit users trying to catch or transfer between buses, as buses are also less likely to wait for passengers if pedestrian/bike crossing wait times are perceived as too long. (10)
- Metro: Regional Transportation Plan, http://www.metro-region.org/article.cfm?ArticleID=137 January 2, 2007.
- National Transportation Operations Council, “National Traffic Signal Report Card, Executive Summary”, http://www.ite.org/reportcard/NTS_ExecSummary.pdf February 8, 2007
- United States Department of Transportation, “Intelligent Transportation Systems for Traffic Signal Control, Deployment Benefits and Lessons Learned.” Project number FHWA-JPO-07-004, January 2007.
- “Show me the Money, A Decision-Maker’s Funding Compendium for Transportation Systems Management and Operations.” Public Technology Institute, National Transportation Operations Coalition, US Department of Transportation, and Federal Highway Administration, December 2005. http://www.pti.org/docs/Trans_Funding_PTI_FHWA_2006.pdf
- “Regional Concept for Transportation Operations (RCTO) Stakeholders Meeting, Signal Timing Projects, Oakland County, Michigan.” SEMCOG, June 21, 2006. http://www.semcog.org/TranPlan/Operations/assets/RCTO_SignalRetimingProjects_OaklandCounty.ppt#256,1,Regional Concept for Transportation Operations (RCTO) Stakeholders Meeting. Signal Retiming Projects Oakland County, Michigan
- Halkias, John, and Michael Schauer. “Red Light, Green Light.” USDOT, Federal Highway Administration. Public Roads, November/December 2004 Vol. 68, No. 3. http://www.tfhrc.gov/pubrds/04nov/07.htm
- “Traffic Signals Optimization.” Climate Trust Website, http://www.climatetrust.org/offset_traffic.php
- “Congestion Mitigation and Air Quality Program (CMAQ).” Chicago Area Transportation Study website, http://www.catsmpo.com/prog-cmaq.htm
- “2007 Regional Signal Timing Program.” San Francisco County Transportation Authority website, http://www.sfcta.org/content/view/255/8
- City of Vancouver, British Columbia, “Policy Report, Traffic and Transit.” June 5, 2001. http://www.city.vancouver.bc.ca/ctyclerk/cclerk/010605/tt3.htm
- “Signal Clearance Timing for Bicyclists”, Alan Wachtel, John Forester, Gary Foxen and David Pelz.
- City of San Francisco, California, “Bicycle Plan - Part 5, Recommended Design Standards.” http://www.ci.sf.ca.us/site/bac_page.asp?id=11542#P102_12565
- “Signal Clearance Timing for Bicyclists”, Alan Wachtel, John Forester, Gary Foxen and David Pelz.
- “Cross-Jurisdictional Signal Coordination, Case Studies.” Federal Highway Administration, USDOT, February 2002. http://ntl.bts.gov/lib/jpodocs/repts_te/13613.html
- “Traffic Signal System Improvement Program, 2003 Update.” Denver Regional Council of Governments, July 16, 2003. http://www.drcog.org/documents/TSSIP_Report.pdf
- Institute of Transportation Engineers, “2007 National Traffic Signal Report Card”, http://www.ite.org/reportcard/ 1/13/08.