Traffic Signal Management Plans

Chapter 1. Purpose of this Guidebook

Introduction

Overview

Research has shown that in effective traffic signal programs there is a strong connection between doing what's most important in the context of limited resources and the extent to which its activities are planned ahead to achieve specific objectives (FHWA, 2009). This research has shown that the extent to which an agency provides good service to its community is not necessarily directly related to the prevalence of resources. Some well-funded agencies are not high performers, while some agencies that are not well funded provide a high standard of service within their acknowledged constraints and in accordance with their plan. A common thread that exists amongst high performing agencies is a demonstrated ability to align and plan the design, operations, management and maintenance activities, and the ultimate replacement of traffic signals (NTOC, 2012).

This guidance establishes a framework for developing traffic signal management plans (TSMP) based on knowledge transferred from a number of archetypical traffic signal programs. A TSMP is intended to document and connect, at a high level, the goals, objectives, strategies and performance measures that an agency uses to achieve outcomes consistent with doing what's most important given a limited set of resources. This guidance will help practitioners strategically connect their activities related to traffic signal design, operations, maintenance, and management with the goals and objectives of their agency. The result will be an objectives-driven TSMP that:

• Provides a succinct description of all activities required for agency staff to manage the traffic signal program.
• Offers a basis for introducing new staff to the processes relevant to their roles, both inside and outside the program or agency.
• Illustrates to management and outside funding agencies the structured approach to traffic signal management.
• Specifies an approach to strategically shift maintenance, operation, and design from reactionary to proactive and to effectively plan for needed capital improvements.
• Outlines an approach for identifying how to deliver good basic service (defined below).
• Helps to provide direction to a large and complex program (in the presence of plentiful resources).
• Identifies programmatic objectives supported by existing activities.
• Improves support for the traffic signal program both within and external to one's agency.
• Aids in mitigating the risks of the program underperforming and not meeting one’s objectives.
• Supports succession planning.

Should You Invest Time in Developing a Traffic Signal Management Plan (TSMP)?

Ask yourself the questions in Figure 1. If you answer yes to any of them, your agency is a candidate for a TSMP.

Figure 1. Would a traffic signal management plan be helpful for my agency?
Source: DKS

It is clear from the results of the national traffic signal report card survey (NTOC, 2012) and other research that very few agencies have a comprehensive plan covering the full lifecycle of design, operations, management, maintenance and ultimate replacement of traffic signals. Moreover, those agencies that do have operating and management plans very often have not clearly linked their objectives to the livability and mobility goals and objectives of their agency or regional planning authority. A strategic approach is needed in order to effectively garner support for and resources to improve the state of traffic signal systems.

Based on FHWA’s broad experience with agencies across the country, it has also become clear that agencies that have some form of strategic plan that covers their traffic signal system also have a high level of performance in the management of their traffic signal system. Moreover, this seems to apply regardless of the level of resources available for traffic signal management. Many resource-rich agencies do not provide great service, while other relatively under-resourced agencies provide very good service within their constraints.

The TSMP connects the goals that appear in agency and regional plans with objectives and strategies that support day to day traffic signal design, operations maintenance, and administrative activities. The TSMP supports an agency's general plan or strategic plan, in a manner similar to an ITS plan, pedestrian master plan or a bicycle master plan, and lays the foundation for development of traffic signal capital improvement plans. Many agencies have existing procedures and policies that feed into the information in the TSMP. Figure 2 shows the relationship between the different documents an agency may have.

Figure 2. Graphic. Relationships among agency documents.
Source: DKS

Good Basic Service and Program Reliability

The mission of a traffic signal program is to provide good basic service that satisfies the goals of the agency and regional partners involved in transportation systems management and operations (TSM&O). Good basic service is defined as doing the most important things given a set of resources. The definition of "important" is up to the agency to determine, but should match closely with user expectations. Traffic signal programs that do not align their objectives with agency and regional goals may encounter difficulty in attracting and sustaining resources to adequately design, operate and maintain traffic signal systems. Achieving good basic service requires implementation of strategies (operations, maintenance, and design) that work together to optimize the program, along with a clear understanding of their objectives. Figure 3 illustrates how the different aspects of managing a signal system all need to work together. If an agency is weak in one area, the stool will be unbalanced, meaning the other two areas need to compensate to remain balanced. For example, if detection is not maintained well, the signal will continue to operate, but the signal timing will need to be adjusted in order to serve the users. If an agency is not performing well in all three areas, the stool will collapse and good basic service will not be provided.

Figure 3. Good basic service components.
Source: FHWA

Program reliability is a measure of an organization’s ability to sustain good basic service. Sustaining good basic service is dependent on:

• Articulating objectives clearly.
• Having expert, committed staff.
• Documenting processes.
• Optimizing process effectiveness.
• Applying systematic processes to inform hardware and software procurement.
• Having predictable resources (capital and operating funds).
• Measuring performance in a meaningful way.

The TSMP connects the activities related to traffic signal design, operations, maintenance, and management with the goals and objectives of your agency. This will guard against the impacts of losing key staff, reductions in critical funding, or both.

Achieving good basic service will involve recognizing the interactions between the different actors, systems, and policies and procedures of your organization. Recognizing those interactions will help generate the appropriate mix of operational, maintenance, design and enabling strategies that agencies will need to keep the stool balanced. This concept is illustrated in Figure 4.

Figure 4. Notable interactions needed to achieve good basic service.
Source: FHWA

The Objectives-Driven Process

The TSMP is based on an objectives-driven, performance-based approach. This type of approach focuses on system performance to measure success rather than the number of activities implemented. The basis of this approach is the development of goals, context, objectives, strategies, and tactics (G-COST). The relationships between goals, objectives, strategies, and tactics are illustrated in Figure 5.

Figure 5. Graphic. Goals, context, objectives, strategies, and tactics (GOST) pyramid.
Source: FHWA

Goals

A goal is a broad statement that describes a desired end state. It is the "what" an agency is trying to achieve. Goals can address different aspects of the transportation system: reliability, efficiency, quality of service, preservation, etc. In many cases, the goal statements for a TSMP can be directly extracted from existing agency policy documents, such as a regional transportation system plan, related master plans such as bicycle and pedestrian master plans, and the transportation element of a city's general plan or master plan.

Here are some examples of agency goals:

• Maintain the transportation system in the most efficient manner.
• Provide mobility for all ages and abilities and for all areas of the community.
• Facilitate efficient transit operation on arterial roads.
• Preserve infrastructure.
• Optimize mobility.

While goals describe a desirable end state, they are not directly "actionable." That is the role of objectives.

Context

While a goal can lead to many different objectives that may apply to a variety of activities (e.g., "livability" may be supported by transportation, libraries, parks, urban design and architecture, sports facilities, and landscaping), the administrative context of the plan and the physical context of the signal operation define the types of objectives that are appropriate in several ways:

• Only objectives that will lead to activities associated with the traffic signal system need to be considered.
• The selected management objectives need to acknowledge the geographical, social, and institutional context within which the plan will operate.
• The operational objectives that define how the signal system controls traffic and other road users need to be consistent with traffic patterns, mobility demands, road network topology, and adjacent land uses.

Objectives

An objective is more specific and measurable and is defined as "what" needs to be done in order to achieve a goal. Although in transportation planning, developing such aims has often been discussed together with goals (e.g., "developing goals and objectives"), it is important to make a critical distinction between goals and objectives within a performance-based planning and programming approach. Whereas goals relate to the "big picture" or desired end-result, objectives should be specific and measurable and support the achievement of a goal.

The most important aspect of identifying these overarching targets is that they be absolutely clear and "actionable." All objectives should include or lead to development of a performance measure that is able to validate achievement of the result, and to support decisions necessary to help achieve each goal. The aims of the TSMP may relate to multiple strategies within the traffic signal program in the areas of maintenance, design, management and operations.

Example TSMP objectives, extracted from some recent TSMPs include:

• Provide facilities at traffic signals to safely and efficiently accommodate all road users (including transit, pedestrians and bicycles in addition to other vehicles).
• Support signal operations that are appropriate for the current traffic conditions and consistent with current operational policies.
• Operate traffic signal system at its maximum efficiency within the context of a balanced, multimodal operation, as described in current operational policies.
• Undertake maintenance in a cost-effective manner.
• Coordinate cooperatively with neighbor agencies to develop and implement regional solutions to traffic problems related to regional issues.
• Design traffic signal system elements that are sustainable in a fiscally responsible manner.
• Preserve the traffic signal system so it always operates as intended.
• Sustain a traffic signal infrastructure that is appropriate for accommodating current mobility goals.
• Inform and educate all stakeholders of the challenge to maintain a modal balance and superior service.
• Keep the community fully informed about the development and operation of the traffic signal system so they understand what we do and why we do what we do, so they can judge for themselves how well we are satisfying their needs.
• Increase traffic flows.
• Improve capacity allocation.
• Advance pedestrian service.
• Enhance bicycle service.
• Create a high level of reliability of detection.
• Maintain fully functional preemption.
• Minimize pollution and noise.
• Retain a complete history of traffic volumes for use in planning, design and operations analysis.
• Develop origin-destination data.
• Further safety-related objectives.
• Reduce time to return intersection to full operation after incident or fault.

It is also important to clearly state the operational strategies one intends to employ in various situations, such as:

• Smooth the flow of traffic along coordinated routes when the system is below saturation.
• Maximize the throughput of vehicles along coordinated routes when conditions are at or above saturation.
• Equitably serve adjacent land uses when throughput is not the objective.
• Manage queues to prevent excessive queuing from reducing efficiency.
• Maximize intersection efficiency at critical isolated (non-coordinated) intersections.

Strategies

A strategy is defined as a capability put in place to achieve an objective. This is where you have the opportunity to be innovative, and also identify strategies that are achievable and sustained within your agency’s existing level of capability. Example strategies found in some recent TSMPs include:

• Undertake proactive maintenance.
• Undertake reactive maintenance.
• Administer maintenance to provide all required capabilities.
• Design signals to support maintenance.
• Design signals to support operations.
• Design signals to accommodate all modes.
• Operate signals to maximize system efficiency.
• Provide signal coordination where suitable.
• Operate signals to safely and efficiently accommodate all users.
• Operate signals to optimize intersection efficiency.
• Operate signals in coordination with regional partners.
• Automate traffic counts.

Each of these strategies has a different effect on one or more of the following:

• Quantity and allocation of resources.
• Documentation of processes.
• Capability of staff.
• Systems and technology.
• Procurement processes.
• Performance measurement.
• Leadership.
• Collaboration, both internal and external.

Tactics

A tactic is the specific method to implement a strategy. It is an action taken (activities) or tool used to help implement the strategies in order to achieve objectives and attain goals. For example, in response to the objective of maintaining a high level of reliability in detection, these may be some appropriate strategies:

• Provide proactive maintenance, to minimize the risk of detector failure.
• Provide reactive maintenance, to quickly repair failed detectors.
• Design signals with types of detectors that are less prone to damage.
• Design signals with fewer detectors to reduce the total number of failures.

To implement these strategies, several entirely different tactics could be considered, which may include the following:

• Strengthen the pavement when loops are installed to minimize the risk of loop failure due to pavement deterioration.
• Use loops protected by conduit and buried deeper than regular, saw-cut loops.
• Use alternative technologies to inductive loops that are not affected by pavement condition.
• Limit the use of detectors to left turn phases.
• Provide equipment and training so staff can quickly repair failed loops.
• Retain an on-call contractor capable of quickly repairing failed loops.

Each selected tactic has a different effect on one or more of the following and needs to be considered and either accepted or discarded:

• The quantity and allocation of maintenance resources.
• The efficiency of traffic signal operation.
• The level of service provided to the road users.
• The cost of installation of traffic signals.
• The accuracy of vehicle detection.

It may be that each of these tactics will be applicable for an agency to use in one or other situations. For example, if an agency has a preference for standardization (often driven by a belief that maintenance will be more efficient if there is less variation in equipment and procedures), the real and perceived benefits of that standardization should be first weighed against foregone opportunities that would result from not picking the tactic that would most effectively address each situation.

Documentation

At the end of the day, all your activities need to be documented so all relevant staff know exactly what they should do and when they should do it. Documenting activities encourages close examination of changes to procedures, ensuring changes represent improvements when they do occur. Ad hoc activities should eventually be formalized and documented, so for the purposes of the TSMP they should be included in an action plan to ensure they are enshrined in your agency’s procedures, are consistently implemented, and will not be lost or abandoned as key staff change.