Improving Traffic Signal Management and

Operations:  A Basic Service Model

Prepared by:

  

Booz|Allen|Hamilton

Iteris

Prepared for:

Federal Highway Administration

Washington, D.C.

DECEMBER  2009

FHWA‐HOP‐09‐055
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NOTICE 

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Technical Report Documentation Page 

1. Report No. 

FHWA-HOP-09-055 

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle 5. Report Date: December 2009

Improving Traffic Signal Management and Operations: A Basic 

Service Model 6. Performing Organization Code 

7. Author(s)

Richard W. Denney, Jr. PE, Iteris 

8. Performing Organization Report No.

 Project 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

Booz | Allen | Hamilton 

8283 Greensboro Drive 

McLean, Virginia 22102 

and 

Iteris, Inc. 

107 Carpenter Dr. Ste 230 

Sterling, VA 20164 

11. Contract or Grant No.

Contract No. DTFH61-06-D-00006 

13. Type of Report and Period Covered

Final Report 

December 2008 – December 2009 

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Highway Administration 

Office of Operations 

1200 New Jersey Ave, SE 

Washington, DC 20590

14. Sponsoring Agency Code

HOP 

15. Supplementary Notes

Eddie Curtis, Contracting Officer’s Task Manager, FHWA. The project team acknowledges, Paul Olson, 

FHWA and Edward Fok, FHWA for their contributions to this report. 

16. Abstract

This report provides a guide for achieving a basic service model for traffic signal management and 

operations. The basic service model is based on simply stated and defensible operational objectives 

that consider the staffing level, expertise and priorities of the responsible agency. The report includes a 

Literature Review, which provides a review of the National Traffic Signal Report Card and SelfAssessment, case studies based on agency archetypes that provide an understanding of how agencies 

deliver traffic signal management services based on their resources and interviews with acknowledged 

leaders providing support for the basic service concept. 

A discussion of signal timing versatility in support of the role it plays in providing good basic service is 

included in the Appendix. 

17. Key Words

Signalized Intersections, Traffic Signal Timing, Staffing, Traffic 

Signal Operations, Maintenance, Management, Objectives, 

Performance Measures 

18. Distribution Statement

No Restrictions. 

19. Security Classification. 

Unclassified 

20. Security Classification. (of this 

page) Unclassified

21. No. of Pages

47 

22. Price

 N/A 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized 

 
 

Table of Contents 

Notice and Quality Assurance Statement

Technical Report Documentation Page

Acknowledgments

About this Report

I. Background

II. Literature Review

GAO Report to Congress and the ITE Toolbox

Traffic Signal Report Card and Self Assessment

III. Case Studies

Agency Archetypes

Archetype 1. High-Activity Response to Adequate (Staffing) Resources

Archetype 2. Infrastructure-Rich Response to Abundant (Capital) Resources

Archetype 3. Well-Managed Response to Limited (Capital & Staffing) Resources

Archetype 4. Insufficiently Managed Response to Limited Resources

Archetype 5. Special Issues with Highly Dispersed Infrastructure (Typical State Agency)

Features of Successful Archetypes

Basic Service Concept

Field Infrastructure Reliability

Minimizing and Balancing Congestion

Smooth Flow

Predictable and Consistent Response

Signal Timing Versatility

IV. Interviews

Local Agency Traffic Signal Program Manager

State Agency Traffic Signal Program Manager

Observations

V. Implementing a Basic Service Concept: The Traffic Signal Management Plan

Clarity of Objectives

Attainable Performance Measures and Standards of Performance

Field Infrastructure Reliability.

Signal Timing

Objective-Based Resource Allocation

Clear Communication Up the Line

Meaningful Systems Engineering

Sample Outline for a Traffic Signal Management Plan

Chapter 1. Objectives and Requirements.

Chapter 2. Responsiveness to Citizens, Media, Policy Makers, and Elected Officials

Chapter 3. Maintenance Strategies to Achieve Objectives

Chapter 4. Operations Strategies to Achieve Objectives

Chapter 5. Design Strategies to Achieve Objectives

Appendix 1. Signal Timing Versatility Concepts
 
 

Acknowledgments 

This work reports on interviews conducted with experts who spoke from experience managing 

large and successful agencies. In order to provide the most candid responses, we have agreed 

not to identify them in this report, but we appreciate their wisdom and candor, and their 

willingness to discuss their day-to-day reality with the researchers. 

The work also benefited from the expert review of FHWA subject-matter experts, including Paul 

Olson and Ed Fok (in addition to Eddie Curtis). The researchers appreciate their integrity in 

advocating for and tirelessly promoting good traffic signal management within agencies. 
 

About this Report 

Over the last several decades, the gap between the state of the art and the state of the practice 

in traffic signal operation has grown. Influential studies such as the 1994 General Accounting 

Office report to Congress have reported improved technological capabilities that go unused in 

agencies that increasingly find it difficult to meet the expectations of policy makers and the 

public. 

Managing the expectations of the agency managers and decision makers to coincide with the 

purpose and objective of traffic signal operations has become an increasingly more difficult task 

for experienced practitioners and traffic signal system managers. The lack of clearly stated 

operational objectives may contribute to an unrealistic expectation that traffic signals can create 

capacity, when in fact they can only distribute it. Yet signal operations activities such as retiming 

projects and traffic signal infrastructure projects are most often proposed by those same 

practitioners to meet the expectation of relieving congestion. 

The perceived gap between art and practice has led to a number of assessment efforts. In 

addition to the industry councils that led to such documents as the Institute of Transportation 

Engineers (ITE) document A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility, 

and external assessments such as the GAO report, more recent efforts have included the Traffic 

Signal Report Card and Self Assessment. All of these efforts reinforce the assumption that 

activities are the measure of effectiveness. Thus, agencies seek to demonstrate that they are 

doing all they can to alleviate congestion by undertaking prescribed activities, including projects 

to retime traffic signals and projects to enhance the traffic signal infrastructure. These activities 

often consume more resources than are available to the agency, with the result that they 

dominate the agency's attention and priorities. By promising results based on activities alone, 

agency professionals often undermine their own credibility by setting unattainable expectations 

and then spending resources in competition with more attainable objectives. 

The industry often promises what it cannot deliver, and then fails to deliver what it could, 

with better commitment and resources. 

In this report, the research team has adopted a different approach. By identifying archetype 

agencies and then gathering information from real agencies, the researchers have attempted to 

define what makes an agency more successful with or without an abundance of resources. The 

report suggests that more successful agencies are those that establish and maintain a concept 

of good basic service. This concept becomes the basis for how they interact with the public, how 

they promise results to policy makers, and how they set priorities for limited resources. It 

focuses on results rather than activities. 

The report begins with a background discussion and a review of the literature, particularly past 

assessments and focusing on the Traffic Signal Report Card. 

Following the literature review, the report develops case studies based on archetype agencies. 

These archetypes illustrate the different levels of resources and how those resources are used, 

whether the agency looks good in assessments and whether it gets results in terms of motorist 

and policy-maker expectations. From these archetypes emerges the concept of good basic 

service. Targeted interviews with two agency managers provide examples of how well-regarded 

agencies define and achieve their goals (or not). 

The interviews and the archetypes then form the basis for developing a basic service concept, 

including the outline for a Traffic Signal Management Plan for traffic signal operating agencies 

consistent with that basic service concept. 
 

The Appendix includes a discussion of signal timing versatility and how the objective of 

versatility contrasts with the more common objective of optimality. 
 

I. Background 

Through the 1950's and 1960's, the technology and novelty of automatically controlled traffic 

signals led the agencies that owned and operated them to develop extensive staff capabilities to 

support their effective operation. Considerable resources were devoted to the development of 

guidelines and underlying research, leading to the common result that agency professionals 

held a high level of expertise and esteem within their agencies. 

As traffic signals have become ubiquitous, their operation and management has emerged from 

a novel program receiving special emphasis to what appears to be a commodity. Agency 

professionals are less likely to be nationally known experts, less likely to be sent to national 

conferences where they can learn from their peers, less likely to be supported with society 

memberships such as in the Institute of Transportation Engineers, and less likely to have direct 

access to and the unconditional respect of policy makers and elected officials. This trend has 

led to a feeling of embattlement on the part of highly competent agency professionals, who are 

asked and sometimes demanded to do more with less as a matter of routine. The frequently 

seen turnover of elected and policy officials masks the effects of increasing demands even as 

such demands lead to a breakdown of agency effectiveness. This decline in agency regard 

mirrors the decline in other infrastructure-support elements within state and local governments. 

Professional groups, both organized and ad hoc, have discussed these issues at length, and 

many methods have been proposed and attempted to bring greater public emphasis to the 

problem of declining support for traffic signal operation. In all cases, these efforts are hampered 

by the inability to easily measure the performance of the signal operation, lack of clarity as to 

the objective of the signal operation, and a simple understanding of how to achieve those 

objectives. Without clear goals and an equally clear plan to achieve those goals, agency 

professionals find it more and more difficult to articulate their resource needs within their 

agencies; even those needs critical to providing good basic service, let alone advanced 

capabilities. The various facets of this generalized characterization are vast. And despite that 

the characterization is a generalization, all agency professionals feel the pressure of trying to 

maintain good basic service in light of declining resources and credibility. 

These trends have coupled with increasing urban populations and resulting increases in traffic 

congestion, which has undermined faith in the ability of traffic engineers to achieve real 

improvements. Agency professionals are often left with a losing proposition—to try to minimize 

the rate at which traffic conditions worsen, both as a result of increased demand and as a result 

of reduced field equipment maintenance. 

The FHWA has the difficult task of supporting state and local agencies in their attempts to 

improve their ability to achieve better results. The reasons for this difficulty can be summarized 

as follows: 

1. There is no consistent and defensible standard of good operation. 

2. Measuring performance to test against a standard often requires unattainable resources. 

3. As resources have declined, so have the ability of agencies to attract, develop, and 

retain true experts. 

4. Many agencies depend on consultants to fill their expertise gap, but the turnover of 

consultants available to do such work is at least as high as the turnover within the 

agencies. This undermines attempts to improve the competence of practitioners through 

federally sponsored training, for example. The pool of consultant engineers with no 

agency experience continues to grow, in many cases widening the expertise gap. 
 

5. Without a definition of good operation, there is no standard of good maintenance that is 

generally enforced. 

6. Clear objectives and plans to achieve those objectives are not technical problems, yet 

the research community often focuses on technical issues, sometimes at levels far 

beyond the daily reality of practitioners. Research often focuses on technology to 

provide the solution, with many researchers believing that the hopelessness of 

developing proper standards and resources requires that meeting such standards will 

depend on expertise built into automated systems. 

7. Practitioners often have difficulty providing agency policy makers and elected officials 

with a clear view of progress towards operational goals, and therefore are leaving them 

with a reluctance to fund improvements. Often practitioners who should provide this 

clarity feed the problem by not effectively managing expectations or by over-promising 

results in support of their projects. The classic example is the defense of traffic signal 

systems on the basis of performance measures wholly related to improved timings, 

without the recognition that improved timings can be implemented without the system. 

Thus, systems are not justified by the true needs, which are based on managing field 

infrastructure as opposed to attaining specific traffic performance improvements. 

The FHWA has promoted a number of efforts designed to measure and improve the situation. 

The Traffic Signal Report Card, which was conducted by the industry in support of a major 

FHWA initiative, showed generally poor results around the country. But those results were often 

based on effecting positive outcomes by completing a variety of activities, or by maintaining 

arbitrary ratios such as the frequency with which signals are retimed or the number of 

maintenance technicians on staff. 

FHWA also has supported the development of a range of training programs, including National 

Highway Institute courses on computerized traffic signal systems and on traffic signal design 

and operation, and on Internet-based courses such as on traffic signal timing. These courses 

help, but they must be part of an overall program to evaluate, reward, and maintain the 

professional capacity of agency staff. Often, the students of these courses have little authority to 

implement the recommendations offered, and the policy makers who do have that authority are 

rarely involved. 

More recently the FHWA has developed a Traffic Signal Timing Manual and is currently 

promoting the formation of Regional Traffic Signal Management Programs. Regional 

collaboration allows signal operators to leverage the expertise and resources within the region 

to clearly articulate operations objectives and performance measures that resonate at a region 

level often attracting support for and investment in the management and operation of signal 

systems. 

Making progress in the context of these very difficult issues is a tremendous challenge, both 

technical and organizational. Organizational improvements must support technical 

improvements, and technical improvements are necessary to meet organizational objectives. 

Instilling those objectives and improvements will require achieving a clarity of understanding 

concerning where traffic signal management should be hopeful and where expectations should 

be moderated. 

The industry often promises what it cannot deliver, and then fails to deliver what it could, 

with better commitment and resources. 
 

II. Literature Review 

GAO Report to Congress and the ITE Toolbox 

In March, 1994, the General Accounting Office published a report to the Chairman of the House 

of Representatives Energy and Commerce Committee. That report was titled, Transportation 

Infrastructure, Benefits of Traffic Control Signal Systems Are Not Being Fully Realized. That 

report was motivated in part by a 1990 review conducted by the Federal Highway Administration 

that found that 21 of 24 traffic signal systems did not meet minimum standards of performance. 

That assessment, titled Operation and Maintenance of Traffic Control Systems, was motivated 

by the Institute of Transportation Engineers publication A Toolbox for Alleviating Traffic 

Congestion and Enhancing Mobility, which had documented that many local agencies were 

installing systems without considering the cost of proper operations and maintenance. In 1992, 

a panel was convened to review the FHWA Report and make recommendations for 

improvements. These recommendations led to the establishment of federal funding for 

operations and maintenance, which was included in the ISTEA legislation. 

The following bullets are some of the recommendations that emerged from the ITE panel: 

 Rules and procedures for Federal funding of operations and maintenance. 

 Minimum standards for the knowledge, skills, and abilities required for operations and 

maintenance 

 Guidelines for staffing 

 Model plans for operations and maintenance 

 New training courses covering operations and maintenance 

 Formation of regional traffic management committees. 

 Require state and local agencies to develop staffing plans 

 Require state and local agencies to lead regional traffic management committees 

The additional recommendations (there were 34) were related to traffic signal systems, which 

was the focus of all these efforts. 

The GAO report in 1994 summarized the resulting activities and improvements. The report 

described external issues that contributed to the problem, the main one being jurisdictional 

cooperation. It also described the emerging ITS technologies and how they should be 

incorporated, and it described FHWA's activities in responding to the above recommendations. 

The main weakness of the report is that it did not describe good operation, or establish a 

meaning for good basic service. As such, most local agencies still faced the constraints that 

held them back previously. The Congestion Mitigation and Air Quality Program in the ISTEA 

funding legislation did, however, provide significant new funding for traffic signal systems, and 

ISTEA did provide funding for operations and maintenance for some state and local agencies. 

The conclusion that the capabilities of new signal systems were being wasted was made without 

clearly defining what the needs were for basic operation, and thus without knowing whether 

those features were actually useful in as many situations as the report suggested. Also, the 

report did not determine whether these advanced features really added to the cost of those 

systems. The report was correct in noting (and in summarizing the results of those previous 
 

studies) that agencies were using capital funds to buy technology rather than focusing on good 

basic service. 

In 1997, ITE updated the Toolbox, with considerable expansion to cover emerging ITS activities. 

For traffic signals, the Toolbox included signal timing improvements, updated equipment, 

coordination, removal of unneeded signals, and improved maintenance as tools in the toolbox. 

They provide an estimate of the benefits and costs of these tools, but the report did not attempt 

to define good basic service, or to provide examples or information of how agencies to define 

their own basic service concept. 

Traffic Signal Report Card and Self Assessment 

In 2005 (and then updated in 2007), the ITE under FHWA sponsorship developed a national 

report card identifying the overall effectiveness of signal operations and management. The 

report card was based on a self-assessment process, which itself identifies a range of priorities 

and objectives for agencies by grading agencies on those objectives. 

The contents of the self-assessment include the following categories: 

 Management 

 Intersection signal operation 

 Coordinated system operation 

 Signal timing practices 

 Traffic monitoring and data collection 

 Maintenance 

Each of these categories included general questions on overall programming, but more 

importantly for this review are those questions that reflect specific objectives. The following 

sections discuss each category, with an attempt to determine the underlying objectives that 

might be used to guide traffic signal management. 

Management 

Activities considered important enough to ask about included: 

 Commitment of staff to peak period active traffic management 

 Motorist information 

 Special pedestrian needs 

 Automated active monitoring of traffic flow 

 Ability to respond to planned events 

 Ability to respond to unplanned events 

All of these objectives are based on traffic conditions and control responses. Good management 

was described as including active programs for tracking events, monitoring incidents, and so on. 

None of the questions, however, determined if the agency had an operational objective, other 

than being responsive. The self-assessment, however, does not query agencies concerning the 
 

importance of these activities in their jurisdiction other than a general question of whether the 

agency had an overall operational philosophy. 

Intersection Signal Timing 

Important activities included: 

 Process documentation in place for routine retiming 

 Signal timing database management 

 Routine reviews should include pedestrian volumes, vehicle volumes, and speeds 

 Are clearance intervals and other non-operational timings reviewed routinely? 

 Follow-through of reviews to implementation and fine-tuning 

 Review other control aspects, including the need for the signal, phases, and restrictions. 

 Review railroad operation 

As with the Management category, there is no discussion of whether agencies have an 

operational objective. It does not question whether agencies have a consistent clearanceinterval policy, a consistent pedestrian accommodation policy, etc. It does not make the 

distinction between design signal timing parameters and operational parameters. Design 

parameters include clearance intervals, detector timing, minimum greens, and pedestrian 

intervals which are based on the geometry of the intersection. Assuming a policy was in place 

for calculating these parameters, well-managed agencies might not see the importance of 

reviewing them routinely, except to determine that the intersection geometry has not changed, 

and the signal timings in the controller are the intended settings (which is covered by the 

database management question). 

Coordinated Operation 

Underlying measures of effectiveness in this category include: 

 Reviewing coordination timing at least every three years. 

 Reviewing coordination parameters more often as needed. 

 Timely follow-through following review 

 Optimization software is a requirement of routine retiming 

 Accommodating weekends, holidays, and planned events 

 A policy for when adjacent intersections should be coordinated 

 Coordination should cross jurisdictional boundaries 

 Traffic-responsive or adaptive control is considered the correct response to 

unpredictable demand 

Again, no attempt is made to determine whether these measures really are relevant to strong 

operational objectives. For example, if the objective is to minimize travel time, or, in the absence 

of that, to minimize inequity, then traffic-responsive operation might not be the solution even if 

traffic volumes are not completely predictable. Rather, an agency may properly respond to this 
 

objective by purposely designing signal timings for maximum versatility. A more fruitful approach 

might be to determine if the agency has identified, implemented, and evaluated a strategy for 

responding to situations of unpredictable demand. Given that the concepts of signal timing 

versatility are not well established in the practice, questions may need to be tailored to specific 

approaches that promote versatility, such as bandwidth optimization in response to 

unpredictable demand, which a practitioner might prefer because it addresses a wider range of 

conditions than calculated optimal timings based on a specific, and possibly not representative, 

set of conditions. 

Signal Timing Practices 

Underlying objectives in this category are: 

 Including queue-departure time in progression timing 

 Consider all parameters using software 

 Willingness to vary phase sequence to enhance progression 

 Minimize delay and stops during night-time operations 

 Avoiding turn-lane spillover 

These objectives are the most closely related to the general objective of minimizing travel time 

and providing equitable operation. Several, however, reflect regional practices that are not 

applied everywhere. For instance, before an agency implements variable phase sequence, 

which may be an unpopular or unexpected new operation in that region, agency practitioners 

should determine whether it actually promotes their operational objectives. A key feature in 

these objectives is the implicit assumption that computer optimization is an important part of the 

process. This implies a deep requirement for data collection and management that serves no 

other purpose than feeding the software, and may not be tied directly to agency objectives. 

Thus, the use of practices such as variable phase sequence does not mark an effective agency 

as well as the agency's process of considering whether such practices meet their objectives. 

Traffic Monitoring and Data Collection 

This category implies the objectives of: 

 Collecting, evaluating, maintaining and sharing traffic data 

 Measuring system performance 

 Reporting activity to decision makers, elected officials and the public 

The traffic data collected including turning movement counts in 15-minute intervals, and 

performance data including travel time and number of stops. Again, the data are not directly tied 

to objectives to determine the true importance of the data. 

Maintenance 

The underlying objectives implied in this category include: 

 Responding to emergency maintenance within 1 hour during business hours. 

 Tracking funding with growth, life-cycle replacements, and technological obsolescence. 
 

 Implementing a process to receive, track and respond to citizen complaints. 

 Maintaining high levels of technician training and certification. 

 Reviewing and routine testing of signal equipment frequently (quarterly through annually, 

depending on the review or test). 

 Automated malfunction monitoring. 

 Maintaining high detection functionality. 

 Tracking equipment maintenance trends. 

 Providing emergency power at critical locations. 

These objectives allow agencies to score well if they have well-funded and active maintenance 

programs. Not all agencies have those resources, however, and signal practitioners still must 

respond to their situation as best they can. There is nothing in the self-assessment that allows 

an agency to overcome limited resources by more effective design. For example, an agency 

might achieve more effectively meet their operational goals by minimizing the number of 

detectors and designing their operation in such a way that those detectors are not needed. This 

might be done by limiting the cycle length, providing versatile smooth-flow coordination timings, 

ensuring that clearance intervals are sufficient to minimize the need for dilemma-zone detection, 

and so on. Highly durable detection construction might be affordable if the detection needs are 

minimized, further reducing the demands on maintenance. Consistent design standards (rather 

than high design in some locations that are funded by developers and minimal design in 

locations funded by the agency) can minimize the need for continued maintenance of the 

physical plant. Careful selection of technology might prevent expecting maintenance technicians 

to have skills beyond what the agency can remunerate. All of these strategies for surviving 

limited maintenance resources flow from a careful relationship between operational objectives 

and maintenance realities, but the self-assessment does not credit agencies who exercise such 

care. 

Summary 

The Traffic Signal Report and Self-Assessment was successful at shining the spotlight on the 

need for greater investment in traffic signal operations and maintenance, and providing a 

benchmark of common practices within the traffic signal community. Effectively, the Traffic 

signal report card is a document for policy makers rather than for practitioners, but it does imply 

some global objectives and standards of performance for local agencies that may not always be 

consistent with the realities faced by practitioners. The Traffic Signal Audit Guide also 

developed by NTOC offers an opportunity for practitioners to take a more in depth look at their 

specific practices and to develop process that more effectively meet local objectives. 

When agency professionals are developing and defending their budgets, the Report Card and 

its associated reports and audit guide are most helpful, and collectively these documents 

provide the only real synthesis of expected and good practice. In the end, though, it is a 

diagnostic tool at the screening level, not a clinical approach for a given agency to improve their 

traffic signal management. 
 

III. Case Studies 

Agency Archetypes 

Archetypes of agencies can be used to evaluate the effectiveness of agency practices and 

needs. In this section, we will lay out a range of possible agency archetypes, and then we will 

use these archetypes as the basis for a series of interviews with real agencies. 

Archetype 1. High-Activity Response to Adequate (Staffing) Resources 

Archetype One would be typical of a state or large metropolitan agency that has identified 

operations and maintenance as a core business practice. The business plan for that agency 

supports staffing and resources focused on delivering an operations program. The staff 

undertakes bi-annual signal timing reviews by hiring outside consultants to collect turningmovement counts at all intersections, reviewing all fixed intervals at each intersection, 

developing and programming signal optimization software for calculating optimized signal 

timings, evaluating signal timings using micro-simulation, and providing revised signal timings to 

the agency. The agency has an active program for maintaining the data and making sure it is 

installed and maintained in signal controllers and systems. 

Before any signal timings can be implemented, they must be evaluated using microscopic 

simulation, both by consultant and agency staff. Agency staff are hired with extensive expertise 

in analysis and simulation, and encouraged to improve that expertise through regular training. 

Consultants are hired to work on site, under agency supervision and with no access to highly 

experienced consultants. The operations staff does not have the authority over basic timing 

parameters such as phasing, phase sequence, pedestrian accommodation, detector placement, 

and intersection lane usage. Those parameters are aggressively controlled by other 

departments within the agency. Because of the perceived workload resulting from high activity 

levels, operational personnel also are not encouraged to spend time in the field to observe the 

results of the operation. Using microsimulation was a response to this restriction (and also a 

cause of it). Improvements are reported on the basis of simulation. 

This archetype sets a precedent for for detailed analysis. However, several key weaknesses in 

their situation prevent getting the best results: 

 Not being able to design phase sequence along with signal timing limits the versatility 

and optimality of the results. Often, the phase sequence decisions are made to protect 

as many movements as possible rather than to provide efficient operation. 

 Signal timing technicians and engineers do not have authority over final results, and are 

not encouraged to understand their analysis in terms of on-street performance. 

 Traffic engineering staff and operations staff are not mutually responsive, and some 

operation is controlled by one group while other operation is controlled by a separate 

group. This is quite common in real agencies, where a traffic signal system is operated 

by a different group than the basic signal timing staff that does non-systems operational 

design including phase sequence. 

 Befitting their abundant resources, the agency employs or contracts with a large pool of 

engineers. Those engineers, however, remain separated from maintenance technicians. 

The technicians and traffic engineers do not benefit from any expertise in operations, 

and the operations staff often work in the absence of relevant input from traffic engineers 

and technicians. 
 

 The timing approach is driven by software and the data required by software, rather than 

being driven by performance results on the street. 

 Most of the agency's considerable operations resources are consumed doing data 

collection and analysis, rather than doing on-the-ground performance measurement 

meaningful to the objectives of motorists. 

 The agency does not benefit from hiring consultants, using them as an extension of staff 

rather than a source of expertise. This is reflected by structuring their consulting projects 

to require on-site services, which makes it difficult for consulting companies to commit 

their most experienced experts, and by refusing the pay the rates of consultants who are 

most advanced in their careers. (This report does not attempt to address the problem 

that consultants are not consistently expert despite their rates or stated experience.) 

 The resources and software emphasis reduces the agency's ability to respond to 

special-event signal timing needs. 

 The agency responds to citizen complaints with descriptions of activities they are 

undertaking, rather than with the reasons for the operation being complained about. 

Complaints lead to studies, justifications for system enhancements, revised timings, and 

other activities, but operations staff are not compelled to be able to explain their 

decisions to citizens and their representatives. 

 The agency believes that it is undertaking an aggressive and successful program. 

Archetype 2. Infrastructure-Rich Response to Abundant (Capital) 

Resources 

Archetype Two might be typical of an agency that has committed to improving operations 

through capital programs that supports infrastructure improvements. The agency has not 

garnered support for increasing staffing resources to support active operations; which, 

effectively is a new activity within the agency. The agency has built an extensive centralized 

traffic signal system with downstream detectors at all intersections, adaptively controlled. 

Operations staff is limited but maintenance capabilities are good and capital programs wellfunded. The limited operations staff are used to performing travel time analysis and 

systematically review the network for unexpected queuing. The agency has a defined 

operational mission of providing smooth flow and minimizing congestion, the technicians are 

trained to observe and evaluate the system in accordance with those objectives. The strong 

maintenance capability keeps the extensive infrastructure in good working order. Well-founded 

design standards provide consistent infrastructure (that provides the features needed to achieve 

their operational objectives) and pedestrian accommodation, but without much downstream 

review after construction. 

The agency reviews signal timings yearly by scheduling and reviewing split monitoring in the 

signal controllers, for each arterial system. This allows them to identify non-coordinated 

movements that consistently max out, suggesting the possibility of residual queuing. This is 

accomplished using the two operations technicians on staff. The two staff members work a split 

shift, with one technician working during the morning rush and the other during the afternoon 

rush. The morning technician observes system data for an arterial system Tuesday through 

Friday mornings, and the afternoon technician collects similar data Monday through Thursday 

afternoons. The technicians handle adaptive parameter and new intersection data maintenance 

duties in the middle of the day, when their shifts overlap. Using this approach, they are able to 

systematically review all 175 arterial systems plus a downtown grid each year. The split monitor 

and adaptive data results are summarized and reviewed by the engineer in charge of the signal 
 

program during the same week. Unexpected queuing or anomalies lead the engineer to 

schedule a site visit and a review of the arterial. If a field evaluation cannot rectify the problem, a 

more detailed analysis is conducted using data collection and analysis. 

The focus of agency staff on actual performance observation allows them to be responsive to 

citizen complaints. Complaints are handled by the engineer in charge with input from the 

technicians who review that location. The signal system provides real-time monitoring 

capabilities that allow operations staff to respond substantively to citizen complaints that are 

caused by malfunction. The review technicians are also efficiently used for actual observation 

and assessment rather than for activity-based strategies, such as data collection and analysis, 

which may not always serve their objectives efficiently. 

This agency does not score well on the Report Card because of limited systematic data 

collection and retiming and management that is not focused on real-time human interaction. But 

it shows strong results because: 

 Insufficient operations staff resources are compensated by effective capital expenditure 

on systems that work effectively for long periods without frequent systematic retiming. 

 The agency is focused on performance measures appropriate to motorist objectives, as 

a validation of the ongoing adaptive control. 

 By including pedestrian needs systematically in the design process, the need to be 

responsive to pedestrian requests is reduced down to special cases. 

 The agency designed a system that made use of their strengths (strong maintenance) 

and minimized their weaknesses (limited operations staff). 

Archetype 3. Well-Managed Response to Limited (Capital & Staffing) 

Resources 

Agency Three has limited operations and maintenance staffing and limited capital resources. 

The operations staff is small, but the agency has a well-developed operational objective of 

providing free-flow travel time or equitable operation when that is not possible, as stated in a 

mission: 

Don't make motorists stop, but if you must, delay them as little as possible. 

The agency has difficulty maintaining extensive detection and does not build intersection 

detectors in coordinated systems except on minor-street approaches. The agency also focuses 

on efficient and versatile timing that will operate reasonably even when detectors are not 

working. For example, they limit controller max times based on engineered fixed time operation, 

and they keep cycles short and use the least number of protected phases possible. Design 

favors progression for the predominate through flows. Operations staff are limited but have 

authority over the full operation of the signal, including design and signal phasing. 

The agency reviews signal timings yearly using floating-car studies on each arterial system. 

This is accomplished using the two operations technicians on staff. The two staff members work 

a split shift, with one technician working during the morning rush and the other during the 

afternoon rush. The morning technician collects travel time data on an arterial system Tuesday 

through Friday mornings, and the afternoon technician collects similar data Monday through 

Thursday afternoons. Five runs are made in each direction. In addition to collecting travel time 

data, the technicians review operation by having a time-space diagram available in the vehicle 

to ensure that the signals are operating as designed. The technicians handle timing database 
 

maintenance duties in the middle of the day, when their shifts overlap. Using this approach, they 

are able to systematically review all 175 arterial systems plus a downtown grid each year. The 

travel time studies are compiled during the middle of the day, and reviewed by the engineer in 

charge of the signal program during the same week. Unexpected queuing or other delay noted 

in the travel time studies lead the engineer to schedule a site visit and a review of the timespace diagram. If a field evaluation cannot rectify the problem, a more detailed analysis is 

conducted using data collection and Synchro optimization by consultants. Technicians require 

training in travel time data collection and in observing that signal timing matches time-space 

diagrams, but it does not require expertise in simulation or optimization modeling. 

The agency also built signal systems that provide remote access to local controllers to minimize 

the need for field visits to respond to complaints, but without traffic-responsive or adaptive 

control, which requires infrastructure (both communications and detection) that would have 

prevented agency-wide system implementation. The agency focuses its limited design 

resources on setting clear standards for good design such that pedestrian accommodations, 

phasing, initial timing, and lane utilization are done right at the outset. For example, during 

design, a complete operational review is performed to make sure that each signal phase 

provided is needed, that lane utilization balances capacity with respect to demand, and that 

detection (both pedestrian and vehicular) critical to minimizing the impact of the signal on major 

movements is provided. The design principles favor detection where it serves the objective of 

not stopping cars on the main street, without, for example, the added cost of extensive detection 

on the main street. (A common alternative to these appropriate standards is the use of typical 

designs without evaluating their needs at a given intersections, including but not limited to 

always providing a left turn phases when left turn lanes are provided, not considering whether a 

through lane should really be a turn lane, automatic use of a specific phasing scheme—such as 

8-phase operation with leading lefts—without considering the demand at the intersection, 

providing extensive dilemma-zone detection even on intersections in coordinated systems, etc.) 

Operational staff are limited but have full responsibility and authority for the operation of the 

intersection, including phasing, phase sequence, signal head arrangements, detection, and 

timing. 

While Agency Three's funding is considerably less than Agency One's, they get better results, 

and further they can show that their results are better, because: 

 The agency devotes its limited resources to evaluating the operation based on a clear 

understanding of motorist objectives. The objective of not stopping traffic, for example, 

is directly measured by the low-cost travel-time studies, rather than the costlier collection 

of traffic volumes and attempts to model, based on those volumes, a range of 

performance measures that have not been clearly articulated and are therefore difficult 

to evaluate. 

 The agency developed and then consistently applies design standards consistent with a 

realistic assessment of their maintenance resources. Thus, they don't end up with some 

intersections designed at a high level and others that don't meet adequate standards, 

particularly in regards to detection. 

 The agency designed signal systems consistent with their maintenance and operations 

capability. Their strong, objective-based measurement and evaluation program was 

considered more useful in responding to motorist needs than in providing additional 

automatic traffic monitoring. Systems with more advanced detection and control would 

have exceeded their budget for city-wide installation, and they considered it better to 

have good field device management throughout the agency rather than advanced 

features in a smaller area and no capability elsewhere. 
 

 The agency is highly responsive to citizen input because of their motorist-relevant 

measurement approach and good access to field infrastructure. 

 The versatility of signal timings minimizes the need for additional detection and 

automated responsiveness. 

 Centralized authority over all aspects of design and operation provide the tools 

necessary for versatile signal timing. 

 Consultants are used effectively for situations where new timings are truly needed. 

This agency might not score as well as Agency One on the Report Card, but they get better 

results with respect to their more limited or constrained resources. Those better results are 

reflected in operations consistent with their operational objective—rather than engaging in office 

and computer-based data collection and retiming efforts, they are on the street observing actual 

operation from the perspective of the motorists. The time spent by Agency One staff developing 

simulation models and other volume-based analysis is spent by Agency Three to evaluate 

actual operation in the field, based on measuring travel times directly. And flags for action are 

based on those travel time measurements, which will quickly reveal new congestion, rather than 

on an assumption of need implied by an arbitrary schedule. 

Archetype 4. Insufficiently Managed Response to Limited Resources 

This agency has the same resource limitations as in the previous scenario, but strives 

implement a program of activities without clearly articulating the objectives and outcomes they 

would like to achieve. These activities are accepted as common practice but without clearly 

mapping the activities to local objectives and performance measures the outcomes may not be 

improved. This agency might perform well on the Report Card but not experience the desired 

level of on-street performance for the traffic signal program. The agency opts to hire 

consultants allowing them to apply arbitrary standards for design and operation rather than 

focusing on their limited resources, establishing consistent and adequate design standards and 

operational objectives. The outcome of this approach is expensive, detector-rich installations, 

resulting in fewer intersections being built due to the high costs of construction and 

maintenance. This forces the agency to build some intersections at extremely low cost that do 

not comply with any principles of good design. Thus, some intersections are built with an 

abundance of detection, mast arms, and expensive signal head arrangements, while others are 

built on wood poles using span wire, the minimum number of heads, and no pedestrian 

accommodation. This leads to intersections that must operate poorly to satisfy MUTCD 

pedestrian accommodation requirements. 

Signal timing is performed by consultants without clear objectives, resulting in timings that 

attempt to make the most out of the provided infrastructure. Thus, intersections with extensive 

approach detection use dilemma-zone schemes and long actuated cycles that depend on 

actuation to provide optimal operation. Max times are set long to allow actuation to work. 

Consultants based their design on data collected by the agency, because of limited budgets to 

pay consultants to do so. The two operations technicians on staff are used to set road-tube 

counts and conduct occasional turning-movement counts. Signal timings are developed for all 

arterials on a rotating, five-year program. To improve the effectiveness of signal timing, 

intersection detectors are tasked as system detectors, and arterial systems use trafficresponsive operation. Frequent detector failures greatly reduce the effectiveness of the 

operation, which falls back to programmed daily schedules, but without the agency's frequent 

review. 
 

The large number of detectors at some intersections pose a maintenance challenge, and the 

agency cannot keep the detectors working. Thus, the intersections do not operate effectively, 

with detector failures resulting in long green times and cycles even when demand is low. Limited 

resources preclude the needed reviews of these intersections. 

The only review mechanism is responding to citizen complaints. When a complaint is received, 

the agency attempts to review operation on the basis of detection, even if several intersections 

away. The engineer reviewing each complaint has no baseline travel-time-based performance 

data against which to compare current operation. Signal timings are tweaked to accommodate 

the complaint, but without a systematic review of the whole arterial, which must wait for the next 

signal timing update, those tweaks may undermine the basic versatility of the signal timing plan. 

For example, adjustments to improve intersection splits often undermine progression if the 

progression design isn't considered as part of the adjustment. 

The results achieved by the agency are poor, because: 

 The agency has no performance measurement outside of citizen complaints, let alone 

measurement linked to motorist objectives. 

 The agency feeds analysis software rather than collecting performance data. 

 The agency is reactive rather than proactive. 

 Adjustments made between optimization projects are not made systematically within the 

context of the timing design. 

 The operational picture presented to motorists is inconsistent, with apparent inequities. 

 Operation is usually degraded by the failure of detection, mostly because the operation 

depends too much on the detection. 

Because the agency collects data and performs analysis, it might score better on the Report 

Card than in the previous scenario, though the results will not be as good, because resources 

are not aimed at activities directly linked to performance that matters most to motorists. Those 

activities can be seen as one step removed from operation on the street, as an abstraction or 

representation of that operation, rather than as the definite example. Analysis might show a 

significant improvement in delay, for example, but motorists are more directly concerned with 

how smoothly and predictably they flow through the network. The temptation to depend on 

analysis more than observation overwhelms this agency. 

Archetype 5. Special Issues with Highly Dispersed Infrastructure (Typical 

State Agency) 

Archetype Five is typical of an agency that has limited operations and maintenance capabilities 

due to in adequate capita and staffing resources relative to the number and dispersion of traffic 

signals within its jurisdiction. 

Most of the intersections built by the agency are in remote areas, and coordinated systems are 

on suburban or fringe arterial streets and not grid networks. The arterial networks frequently 

center or cluster around freeway interchanges, including diamond interchanges. 

The key operational constraint on the agency is the distance from the office to the traffic signals. 

Often, a state DOT district office is located in a city that maintains its own traffic signals. And 

just as often, the agency's operations staff must divide their time with many other traffic 

engineering duties, including signs, pavement markings, and liaison with local agencies. 
 

Because of this, these agencies usually seek to make their intersections operate without their 

direct involvement to the extent possible. These limitations lead to a series of broad 

requirements: 

 The operation of the signal must accommodate changes in traffic at all time series, 

including daily, weekly, and seasonal variation in addition to long-term trends. 

 The signal must provide access from the operations staff for observing operation in 

response to citizen complaints, and for making adjustments and maintaining the signal 

timing database. This access is needed on an ad hoc basis. 

 Field reliability is paramount. This requirement is in conflict with the first requirement, 

because accommodating traffic variation over the long run requires detection, and 

detection is the least reliable component of traffic signal installations. 

 Design standards that focus on high-quality installations improve reliability and thus 

minimize the need for future involvement. This includes not only detection, but also the 

physical infrastructure of the signal to support a range of operation (such as using longer 

mast arms than necessary to ease the installation of future left-turn heads). An agency 

with more signals closer to their office might be able to adopt a model that requires 

greater on-street involvement. 

The agency reviews signal timings yearly using floating-car studies on each arterial system. 

Unexpected queuing or other delay noted in the travel time studies lead the engineer to 

schedule a site visit and a review of the time-space diagram. If a field evaluation cannot rectify 

the problem, a more detailed analysis is conducted using data collection and Synchro 

optimization by consultants. Signal timing is designed expressly to provide the maximum 

potential for through-band progression. Given the fringe suburban setting of their systems, 

severe congestion is rare, but rapid growth means that variability is high and such versatility 

maintains acceptable operation in the face of such variability. 

The agency also built signal systems that provide remote access to local controllers to minimize 

the need for field visits to respond to complaints, but without traffic-responsive or adaptive 

control, which requires infrastructure (both communications and detection) inconsistent with the 

long distances to the office. The agency focuses its limited design resources on setting clear 

standards for good design such that pedestrian accommodations, phasing, initial timing, and 

lane utilization are done right at the outset. Operational staff are limited but have full 

responsibility and authority for the operation of the intersection, including phasing, phase 

sequence, signal head arrangements, detection, and timing. 

Agency Five uses the detection infrastructure, and the ability of their systems to give them 

access to the field equipment to minimize the effect of such large distances to the signals from 

their office. Thus, they get good results: 

 The agency devotes its limited resources to evaluating the operation based on a clear 

understanding of motorist objectives. 

 The agency applies design standards consistent with a realistic assessment of their 

maintenance resources. For this agency, that means high-quality installations to 

minimize maintenance visits, which for them is a more important measure than 

maintenance skill. 
 

 The agency designed signal systems consistent with their maintenance and operations 

capability. Their need to monitor conditions remotely, and to effectively manage the field 

infrastructure remotely is well accounted in their design. 

 The agency is highly responsive to citizen input because of their motorist-relevant 

measurement approach and good access to field infrastructure. 

 The versatility of signal timings minimizes the need for additional detection and 

automated responsiveness. 

 Centralized authority over all aspects of design and operation provide the tools 

necessary for versatile signal timing. 

 Consultants are used effectively for situations where new timings are truly needed. 

Features of Successful Archetypes 

The archetypes above that are successful present the following features: 

 Strong concept of basic service. In the face of limited objectives, the effective 

agencies place a high priority on providing good basic service first, with less emphasis 

on attempting advanced service models. These agencies have defined what basic 

service means for their agency, and they evaluate their operation in terms of those basic 

services to ensure that they succeed. The ease with which one can construct an agency 

archetype that spends a lot of resources without achieving good basic service 

demonstrates that even good basic service can be a challenging goal. And while the 

Report Card does not distinguish between basic and advanced service, the poor Report 

Card performance suggests that focusing on basic service is not as common as it might 

be. Most agencies have limited resources, and all agencies experience occasional 

resource reductions; the definition of and commitment to good basic service is highly 

recommended. 

 Clear evaluation of objectives. While minimizing travel time might be considered too 

broad by many practitioners, the fact that only Archetype Three responds to limited 

resources by focusing more tightly on that simple objective reveals too little attention to 

those broad objectives. This is closely related to the basic service concept, and the best 

agency models evaluate their effectiveness in terms of basic service objectives first. 

Archetype One conducted extremely detailed analysis, but without on-the-ground 

attention to simply stated broad objectives. Thus, it cannot really know how well it meets 

that objective. 

 Close coordination of design, operations, and maintenance resources and 

limitations. The successful archetype agencies avoid constructing infrastructure 

elements that cannot be maintained, and they avoid operation that demands such 

infrastructure and maintenance. They also avoid overdesigning some intersections at the 

expense of barely meeting minimum standards at other intersections. Or, they purposely 

design systems that demand more capital funding up front in order to respond to a 

limited operational capability of their staff. The relationship between design, operations 

capability, and maintenance resources is the key element of this feature. Each agency 

must develop that relationship for themselves based on the dynamic balance between 

resources and objectives. Increasing infrastructure sophistication may be a good tradeoff in response to limited operations staff. Decreasing infrastructure sophistication may 

be a good trade-off in response to limited maintenance capabilities. An agency should 

not build what it cannot maintain and operate, but sometimes a more sophisticated 
 

design may reduce demand on maintenance and operation. For example, one 

successful archetype used adaptive control to reduce the operations resource 

requirements, but with the recognition that adaptive control placed a greater demand on 

the agency's maintenance capability. An agency limited in both maintenance and 

operations may achieve the best balance by focusing on simple and highly versatile 

coordinated signal timings rather than on detection-intensive designs that result in poor 

operation when the detection fails. And the choice to use simple and versatile timings 

may get more consistently acceptable results rather than depending on analysisintensive timing design which narrows the optimal range and reduces versatility in return 

for marginally better measures of effectiveness as reported by the analysis tools. 

 Good understanding of measuring results. This is related to the strong concept of 

basic service, but it also leads to a better validation process for more advanced service. 

For example, an agency that is spread over a large geographic area (the limitation) may 

design systems that maximize remote monitoring capability (the response), on the basis 

of minimizing the number of required field visits (the measure). An agency that has 

limited staff resources but with high skill levels may more effectively invest in 

sophisticated automated analysis methods, while an agency with a larger staff but with 

lesser skills might need to keep their analysis methods simple, even though they require 

more effort to implement. 

 Commitment to staff development. The strong archetypes seem to better understand 

the capabilities of their staff and do their best to develop staff capabilities and reward 

progress. It should be noted that not all rewards must be remunerative. Agencies that 

provide clarity of objectives and direct methods for evaluating achievement in those 

objectives often observe higher staff satisfaction and enjoyment of their work. And it 

should also be noted that staff development includes a mix of activities, including 

specific training to improve knowledge, mentoring to improve skills and abilities, and 

support for external professional activities such as attending conferences and being 

involved in regional and national technical, policy, and research committees. 

Basic Service Concept 

In this section, the concept of basic service, and how basic service might be evaluated, will be 

further developed. 

As stated in the introduction, any basic service concept must start with the expectations of the 

motorists to whom the service is being provided. Most motorists, when driving their cars (as 

opposed to when they render opinions in the public forum) have some variation on the following 

broad expectation: 

I want to drive to my destination at my desired speed with the minimum of attention and 

interruption. In the absence of achieving that goal, I want to be treated fairly and predictably so 

that I can plan my day with the minimum of uncertainty. 

While such characterizations seem ambiguous, they do lead to a number of clear objectives for 

an agency. These might be: 

 Field infrastructure reliability. 

 Signal timing that minimizes and balances congestion. 

 Signal timing that promotes smooth flow. This objective is an amalgamation of more 

narrowly cast objectives, such as delay, stops, and so on. Actions taken to achieve 
 

those narrow objectives should be evaluated in terms of broad objectives. Delay may be 

reduced numerically, but will the action result in smoother flow? This will usually require 

the application of experienced judgment, but not necessarily high levels of technical 

sophistication. 

 Signal operation that responds to conditions predictably and consistently. 

 Versatile signal timing that provides broad-banded solutions rather than being narrowly 

optimized for a specific condition. 

Each of these agency objectives requires a series of fundamental agency requirements to 

support them. These requirements can form the basis for evaluating basic service. 

Field Infrastructure Reliability 

This objective imposes the following requirements: 

 Realistic assessment of maintenance capability. Most agencies are resource-limited 

because maintenance is usually funded by a jurisdiction's general fund, rather than by 

capital funds, and those resources are capped and subject to sometimes fierce 

competition within the local policy and political environment. General fund sources 

include local property and (rarely) income tax, with some programs supporting 

operations and maintenance from the Federal government. Capital funds are supported 

by relatively rich Federally funded construction programs and the sale of bonds. This 

reality, which is usually outside the control of the traffic signal professionals, 

nevertheless requires those professionals to consider how they manage their resources. 

The two main constraints of maintenance resources are technological and quantitative. 

o Technological resource limitations affect the level of technology an agency can 

support on the basis of their salary structure, training environment, general work 

environment, and local labor pool. Of these facets of the problem, only the 

training environment can be modified by the agency on the basis of a policy 

decision at the level of the operational staff. Agencies therefore attempt to train 

their best technicians to handle more advanced technologies, but often then lose 

those technicians to more lucrative employment in often more pleasing work 

environments, especially if such skills are in demand in the local labor pool. An 

appropriate response to this limitation, other than articulating it in hopes of 

broader policy-level understanding and support, is to design infrastructure and 

adopt operational approaches within the technological capabilities of the 

agency's maintenance resources. Another approach might be to devise a 

maintenance concept that rents that capability from a contractor rather than 

trying to respond within the agency's forces. 

o Quantitative limitations abound in traffic signal agencies. Most agencies of any 

size complain that each maintenance technician is spread too thin over too many 

traffic signals, and this complaint is heard even by the most well-funded 

agencies. One approach to responding to this limitation is to reduce the 

complexity of the infrastructure. This is distinct from reducing the technical depth 

of that infrastructure, and focuses more on the number of infrastructure elements 

built. For example, the most vulnerable infrastructure element in any traffic signal 

program is detection. One of the main reasons for the rise in popularity of video 

detection systems, despite questions of their accuracy in certain situations, is 

that they are perceived to be easy to maintain, particularly without having to 
 

block traffic, and easy to reconfigure. A system that can provide effective signal 

timings with less detection can also achieve this objective. 

 Designing within an agency's capabilities. In a forum on operations and maintenance 

held during the late 1980's, Anson Nordby, then the head of the City of Los Angeles 

ATSAC program, observed during a panel discussion that designers often treat each 

system project as an opportunity for a technological tour-de-force. He further observed 

that by doing so, the designers were often leaving the agency's maintenance capability 

behind. The wisdom in this observation suggests that one critical step in any signal and 

signal system design project is a careful evaluation of the agency's maintenance 

requirements. For example, signal designs that require bucket trucks that first-line 

maintenance technicians do not use will require failures of those systems to be 

responded to by second-line resources. This increases the time required to respond to a 

problem, which undermines the basic service objective. Detection again provides 

another example. Many agencies are unable to maintain their pavement as well as they 

would like, and poor pavement usually results in poor in-pavement detector longevity. It 

should be noted that the only way designers will understand maintenance limitations is 

to ask the maintenance staff. 

 Using capital resources to minimize maintenance impact. One approach to the problem 

mentioned above of detector failures in poor pavements is to improve the design and 

construction of the detectors with the poor pavement considered. The City of San 

Antonio, in response to a large number of failed detectors, and in addition to moving to 

operational approaches that minimized the need for detectors, started constructing them 

more durably. They used a 4" rock saw and made a 6"-deep cut. The loop detector 

wiring was enclosed in Schedule 80 PVC pipe, and the loop was placed in a sand bed at 

the bottom of this saw cut. The cut was backfilled with stabilized base (two-sack 

portland-cement concrete) and the wear surface was patched with asphalt. While this 

approach used more capital funds, those capital funds were relatively more available 

than maintenance funds, and the resulting trend was an increasing percentage of 

functioning detectors. 

Minimizing and Balancing Congestion 

One of the recommendations made in the final report for the FHWA project Signal Timing Under 

Saturated Conditions was to devote the agency's best resources to its worst congestion 

problems. Leading practitioners, as reported in that work, recommended: 

 Make use of every available feature, however esoteric, to improve green time efficiency 

in favor of the congested movements. This requirement might be seen as conflicting with 

a realistic understanding of maintenance limitations, but it need not be so. An agency 

can reconcile both these objectives by ensuring that the extreme operational efforts are 

spent wisely and not wasted on intersections that operate routinely and don't need such 

efforts. 

 Devote the agency's best operational experts to the most congested problems, and be 

prepared to support their extended observation and experimentation in pursuit of a 

solution. 

That research also suggested a clear focus on operational objectives as conditions moved into 

the congested regime. During uncongested conditions, the agency should try to provide smooth, 

predictable flow in accordance with the expectations of motorists. When congestion occurs, 

smooth flow is no longer possible, and the agency should switch to an objective of maximizing 

throughput. When demand increases to the point where queuing is inevitable, the agency 
 

should operate the signals to minimize the damage done by queue formation in an attempt to 

keep the problem from cascading throughout the network. 

Following these approaches will, in many cases, provide a balanced approach to congestion 

that most motorists will see as (at least) equitable, consistent with their expectation of good 

basic service. 

Smooth Flow 

Many agencies now use advanced analysis tools to optimize and evaluate traffic signal 

operation. But the optimizations and the evaluation measures are surrogates for the 

"measurements" made by motorists. For example, motorists do not separately measure time 

delayed and time not delayed. They measure total travel time, and travel time reliability. All 

motorists apply a greater penalty to time delayed than time not delayed. But motorists also 

evaluate the cause of the delay when assessing blame, and delay caused by congestion is 

counted less against the agency than delay caused by red lights, especially when the other 

movements of the intersection are perceived to be underutilized. These situations are a leading 

cause of complaint calls. 

The most successful agencies do not blindly optimize based on a narrowly cast objective 

function, such as delay, stops, or some combination thereof. Nor do they optimize solely on 

progression bandwidth. Rather, they provide a mix of operational objectives designed to be 

seen by motorists as fair and predictable. 

For example, progression optimization might find a 10-second band through 20 intersections on 

a four-mile arterial system when using the optimally resonant, say, 90-second cycle. Such a 

progression band might be invisible to most motorists, who fall out of the band at the slightest 

disturbance in the flow, and are then repeatedly delayed until the next band catches up to them. 

Most motorists would perceive better basic service if this arterial was broken up into two or three 

segments, as long as the breaks in progression were clean (such that arriving traffic arrives on a 

long-standing red and not just as the signal is changing to yellow). With such breaks, much 

greater progression bandwidth might be possible. Instead of a large percentage of motorists 

being stopped unpredictably at many intersections, a higher percentage are stopped predictably 

at two locations (in addition to the first). 

Another aspect of good progression design with respect to smooth flow is ensuring that the 

largest entering platoons see the greatest service by the progression band. 

Optimization approaches that minimize delay and stops are often based on simplistic models of 

those stops. If the stops cannot be realistically modeled, optimizing on them is likely to lead to 

distorted results. 

By focusing on good basic service, an agency might forego an abundance of computer 

optimization and simulation, and the numerical data collection that such requires, in 

favor of simple and direct methods that ensure smooth flow, including time-space 

diagrams and on-street evaluation.

Predictable and Consistent Response 

Most highly responsive systems run into the problem of keeping the signals in useful 

coordination while the basic operation is being changed. Adaptive systems control this effect by 

limiting changes to small increments, though this may cause the operation to wander into 

timings that reduce the potential effectiveness of the timings. For example, some adaptive 

control systems allow small changes in the cycle length, even though a given system may 
 

provide good progression on only one or two cycle lengths within the acceptable range (as 

reported by Steven Shelby in his paper Resonant Cycles in Traffic Signal Control,

Transportation Research Record #1925, 2005). Traditional traffic-responsive systems invoke 

often damaging transitions that are usually constrained to occur outside the peak period to avoid 

causing more problems than they solve. This is particularly true of transitions that dwell only, 

with shortway and subtraction transition methods causing less disruption. The transition problem 

suggests that fewer changes of the signal timing plan might be better in many situations. 

Most agencies design only four or five signal timing plans for their arterial street signal systems. 

The range of conditions in any typical day, however, runs the entire gamut from a nearly empty 

network to peak conditions, and from a strong inbound bias to a strong outbound bias. When 

overlaying the range of possible solutions onto this wide range of conditions, most agencies 

divide that solution space into only four zones: Heavy inbound flow, heavy outbound flow, heavy 

balanced flow, and light flow. That suggests that signal timings must cover a broader range of 

conditions than the narrowly defined optimums many computer optimizers would imply. 

Dr. Carroll Messer, author of the seminal PASSER II progression-based optimizer, observed 

during a past conference that broad progression-based solutions provided a predictable

operation. Motorists routinely stop at the same intersections and therefore see the effect of the 

timing solution clearly. When that experience is consistent day in and day out, they can adjust 

their behavior (possibly) or their expectations to that reality. Systems that continuously change 

the motorist experience should be carefully selected when the need for that variability outweighs 

the expectation of a consistent motorist experience. 

Signal Timing Versatility 

Closely related to a predictable and consistent response is the need for versatility in signal 

timing. If the solution space is divided into only four zones, and if that solution space overlays a 

wide-ranging condition space, then each plan in the solution space must provide acceptable 

operation even at the boundaries of the condition to which it is applied. In highly dynamic cases, 

more than four solutions may be required, but that increased dynamic nature still will demand 

versatile signal timing solutions. 

But most computer-based analysis of traffic signals applied by practitioners, both for 

optimization and simulation, considers the traffic demand as a steady state. Thus, signal timing 

approaches are evaluated by their performance during the narrowly unique conditions usually 

characterized by a 15-minute period rather than by the range of conditions over the hours of the 

daily schedule for which those timings will be used, and for the months and years over which 

that daily schedule will be used. The best agencies address this by one of two approaches: 

 Implement a system capable of continuous optimization. That system may use normal 

traffic actuated features at the local controller, including gapping out, hold release, phase 

skipping, and volume-density features. Or it may use a more centralized or regionalized 

adaptive control based on network objectives. In all cases, the effectiveness of the 

system depends on detection. 

 Design for versatility. The best agencies are able to understand signal timing 

effectiveness over a range of conditions by looking at the breadth of the solution rather 

than by seeking a narrow optimum. For example, a progression-based solution that 

works for heavy traffic will also work for light traffic. Even one car in the network will 

move unimpeded. This is a variation on Dr. Messer's observation, that such solutions a.) 

provide a predictable target into which motorists will fit their behavior, and b.) work over 

the broadest range of actual conditions. Agencies that are constrained by resources on a 
 

range of fronts can still maintain good basic service if they consider versatility in their 

methods and solutions. 

Appendix I contains more development of the signal timing versatility concept. 
 

IV. Interviews 

To document current practice and to determine how superior agencies relate to the features of 

the above archetypes to provide basic service, the research team consulted two highly 

respected practitioners, one at the local level, and one at the state level. Because of the desire 

to hear their candid opinions and observations, the researchers have agreed not to report their 

identities directly. 

Questions relevant to comprehensive management are listed below. These questions were a 

guideline for the interviewer, and were not intended to be asked directly to the respondent in all 

cases. The purpose of the interview was to answer these questions, but also to determine if the 

questions were valid or needed to be changed or supplemented. 

1. What does your agency try to achieve? 

2. What principles do you instill in your operations staff? Does complaint response get 

more priority than complaint prevention? 

3. What do you think your motorists expect? 

4. What do you think policy makers and elected officials expect? 

5. Do you consider your operations staff more limited in numbers or in skills? 

6. How do you respond to those limitations and expectations? 

a. Staff improvement? 

b. Staff supplementation (using consultants)? 

c. Productivity standards? 

d. Technological approaches (such as focus on simulation or avoidance of 

simulation)? 

7. How do you know when you are doing a good job? 

8. How much do you feel your operations staff are behind the curve rather than ahead of it? 

9. How do you anticipate successful operations when setting design standards? 

10. What constraints do you face on your ability to maintain your systems? 

11. What do you do to keep your systems working as designed? 

12. How do you define "operations?" 

13. Do you think you are doing a good job? 

Local Agency Traffic Signal Program Manager 

The local agency manager expressed the reality that his staff are always so involved in dealing 

with problems that there is no time to fit their activities into an overall strategy. This is a common 

theme among agencies, and seems more related to perceptions of external expectations than to 

resource levels. 
 

The manager prefers progression when possible, but recognizes that it is not always possible 

because of unresonant spacing and speed. He asks the following general questions when 

reviewing operation: 

 Are we wasting time anywhere? 

 Is delay distributed equitably? 

 Is there green time serving no cars? 

 Imbalanced queuing? 

 Red when there's no competition? 

Versatility is a high priority for the agency, but the manager would like a better means of 

evaluating how versatile is the operation. He has not considered a solution-space-based 

approach to organizing signal timings to ensure fundamental versatility. 

For this agency, complaint response gets priority, of necessity, and because this is the measure 

most sensitive to elected officials and policy makers. 

Motorists expect minimized travel time and the variability of travel time. 

This agency manager believed that elected officials in his jurisdiction had different objectives 

than motorists. His perception was that they preferred not to think about their expectations, and 

only champion causes that affect how they are perceived by their constituents. Consequently 

they seemed generally unwilling to support programs that are not directly responsive to issues 

that are generating current public complaint. 

The manager believed that increased staff would result in improved skills, because currently 

people are overloaded and stuck in reactive mode and don't have the opportunity to learn new 

skills, or to dig into situations so that they can really explore new alternatives. He also observed 

that those who improved their skills left the agency because of frustration related to too much of 

their time is being spent extinguishing brush fires. 

The agency manager believed that they are doing a good job when they receive no complaints, 

but he also evaluated operation in terms of his own standards. But he believed that at the end of 

the day, there is often no good way to evaluate operation. He therefore advocates an automated 

means of observing traffic performance rather than data. He does not, however, have a plan for 

implementing such a capability, though he does advocate for the application of such technology 

initiatives as IntelliDrive to provide a link between vehicles and the infrastructure that would 

provide a description of time and distance trajectories that could be used to construct travel 

times. 

He reports that his staff is behind the curve when addressing issues, with little hope of 

establishing proactive prevention. 

The agency will not use advanced or esoteric controller features based on a realistic 

assessment of maintenance staff. They constrained actuated control by signal timing to prevent 

too much dependence on detection. 

The manager sees imperfect understanding of true operation as the main constraint on agency 

effectiveness. 
 

To ensure that signal timing stays as designed, signal timing settings in the controller are 

reviewed during preventive maintenance. The agency has a goal to drive streets systematically, 

but have never reached that goal, though they have noted improvement in the last several 

years. The time spent addressing complaints, which are managed by a separate part of the 

agency with extreme and vigorously enforced accountability rules, prevents systematic 

observation. 

The manager described "operations" as the non-physical side of the road environment, 

including procedures for creating and modifying signal timings and signal configuration. 

This agency reported a B- on the Signal Timing Report Card, but acknowledged that C+ was 

probably more appropriate. They reported a B- because they felt it was more politically 

acceptable, which the interviewee described as trying to convey that "we're not that good but we 

aren't as bad as most." He believed that the current self-assessment is not too bad, but still a 

little too focused on activities rather than results. 

State Agency Traffic Signal Program Manager 

The state agency requires using a business plan to define goals for activities—to optimize 

certain number of signals per year; deploying advanced systems; response time goals for 

maintenance. 

For example, the agency defines a goal of 5% delay reduction for each optimization cycle, 

which is repeated every three years. This performance goal has had to be downgraded from 

10% because repeated improvements proved elusive. (Author's note: This suggests that either 

traffic demand is increasing beyond what new signal timings can address, or signal timings are 

being redesigned more often than necessary.) 

The agency holds monthly traffic meetings discussing traffic issues and to promote consistency. 

Resource limitations demand that complaint response receives the highest priority, and the 

manager perceives that the agency is always reactive. 

The manager believes that motorists expect consistent, efficient, and safe operation. He prefers 

smooth progression along an arterial, not waiting when there is no demand on competing 

movements, good pedestrian accommodation, and phase protection only when needed. The 

agency maintains a strong concept of progression, preferring excellent progression in shorter 

segments rather than weak progression in longer segments. (Author's note: This requires 

departing from the results attained by software optimization tools currently in use by the 

agency.) 

The manager perceives that elected officials do not want to hear from constituents about lack of 

efficiency and safety. He believes they are also concerned about the responsiveness of the 

agency. 

The manager perceives that his operations staff is more limited in skills than in numbers. 

The agency promotes staff improvement through in-house courses in control devices, which 

they also make available to consultants. For example, they have established a new mentoring 

process for construction inspection, where the designer and inspector are required to work 

together. The agency is trying to capture the skills and knowledge of staff nearing retirement. 

They also provide cross-training, and are trying to provide transparent access to their standard 

procedures. 

The agency supplements staff using on-site consultants and consulting contracts to farm out a 

lot of design. They prefer to use consultants in a supporting role rather than a lead role, based 
 

on the belief that consultants are not good at signal timing, being too dependent on software 

and optimization, and lacking on street experience and insight in dealing with complaints. 

The manager prefers going to the street to review operation rather than engaging in major 

retiming efforts or using advanced analysis tools such as micro-simulation. 

The manager evaluates the program driven by complaints. The agency centrally manages 

signal timing, and believes that getting no citizen complaints means the agency is doing a good 

job. The manager maintains close contact with vocal citizens and believes in handling 

meaningful complaints using the most qualified staff. 

To anticipate successful operation, the agency is doing several things, including replacing span 

wire with mast arms to reduce maintenance; installing LEDs; and using more video detection to 

reduce maintenance needs for in-pavement detection. They already limit detection schemes to 

simple approaches. The manager observed that video is a little more finicky and they are 

working to improve that. The agency's compliance with the Americans with Disabilities Act, 

which dictates pedestrian accommodation at intersections, is dictated by policy, where design is 

outstripping maintenance. The agency cannot afford the staff to be able to participate in the 

one-call program for preventing damage to their infrastructure by utility contractors, and this 

results in frequent damage to their system communications cable. 

Because of resource limitations, the agency does not routinely review signals to make sure they 

are running the intended signal timings. They planned to perform complete optimization every 

three years, followed by annual reviews with a drive-through, but never had the resources to 

keep up with it. 

The manager defined "operations" as timing, phasing, and coordination—anything outside of 

routine maintenance. He observed that designs and design changes are operations-driven 

though done by different people. 

The agency scored a D on the original Signal Timing Report Card, but the manager thought 

questions were slanted to centralized operation and activities, and tainted by design (e.g. 

second-by-second communications). He worked to improve the questions in the selfassessment, but acknowledged that they also had problems—e.g. by evaluating based on ratios 

(number of signals per technician) instead of response time. The agency scored a grade of B 

the second time. The manager claimed they did not game the results, but are still pushing for 

more appropriate questions that focus on outcome more than output. 

Observations 

The results of these interviews reinforce the concept of basic service, but also reveal the 

difficulty even well-managed agencies have in articulating their objectives and designing their 

programs to proactively attain those objectives. 

They also reveal that the initial Signal Timing Report Card focused too much on what 

agencies did rather than what results they attained. 

Both managers complained about the activity orientation of the Report Card. But neither agency 

was able to articulate what they did to measure their actual results. 

Both agencies are driven by complaints in directing their activities, and both managers thought 

this reduced overall performance rather than increasing it. The agency managers did not 

attempt to express philosophies or judgments about the accuracy or representativeness of 

those complaints. It has been the author's observation that wealthy communities generate more 
 

complaints than poor communities, even when the service provided by the agency is better by 

any objective measure. One possible explanation is that citizens in locations that consistently 

provide less service lower their expectations and complaint less often. Thus, measuring overall 

agency effectiveness on the basis of complaint calls might, over time, trend towards a selfreinforcing cycle of lowered expectations and services. If so, then citizen complaints provide a 

strong accountability mechanism to encourage agencies to maintain strong service models, but 

when excessive consume the resources necessary to achieve those service models. The author 

has also observed that agencies have increased accountability for responsiveness to citizen 

complaints. Most agencies maintain a direct tracking system for complaints, expecting the 

response to complaints to be commensurate with the complaint itself (i.e., written complaints 

receive a written response, verbal complaints receive a verbal response, and so on). Both 

agencies devote their best communicators to responding to citizen complaints, primarily to help 

ensure that they neither come back nor escalate. 

Another observation is that even though complaints are the only measure available to 

agencies, they don’t often look for value in the complaint process. For example, if a high 

percentage of complaints result in a maintenance call, then that may signify an inadequate 

maintenance capability. If those maintenance-related complaints are commonly related to, say, 

detectors, that may indicate too much dependence on detectors, and a change in operational 

objectives and approach might reduce the dependence on detectors enough so that motorists 

won't notice when they require maintenance. An abundance of complaints regarding operational 

issues that have to be referred to maintenance forces may also indicate the inability of the 

signal system to allow the complaint responders to diagnose the complaint using the system. 

These trends could therefore lead to a better definition of needs and requirements in support of 

the next system upgrade. Usually, practitioners with experience develop a sense of the nature 

of complaints, but turnover eliminates this built-up understanding. Few agencies have systems 

that track complaints well enough to observe such trends without that experience. 

Both agencies discussed training. The local agency manager complained that staff development 

was hampered by that staff being overburdened with complaint response activities. That agency 

does, however, provide opportunities for staff to become involved with national organizations 

and committees, and thus has maintained a high satisfaction at least for the more motivated 

staff members. The agency has not considered or articulated how it might make use of training 

resources already available, such as courses from the National Highway Institute, in support of 

staff development. 

The state agency has a more explicit training program, and it is the author's general observation 

that this is true around the country. One way in which state agencies may assist local agencies 

with staff development is by sponsoring training programs and then inviting local agencies to 

participate by providing them grants to cover the expenses. The author noted a recent 

presentation of the NHI course Traffic Signal Design and Operation in Ohio that provided grants 

for local agencies to attend, and the course attendance included half a dozen local agencies in 

addition to state participants. State agencies, who generally have more resources to support 

such programs, may find that supporting local agency involvement helps the state agency meet 

its operational objectives as well. 
 

V. Implementing a Basic Service Concept: The Traffic Signal 

Management Plan 

Previously, this report presented the concept of good basic service as a reflection of agency 

archetypes that most effectively focused their resources, however plentiful or scarce, on their 

most important objectives. The interviews revealed that even the best agencies have 

difficulty articulating and maintaining that focus. This section will outline key strategies for 

doing so, and an outline of how to embody those strategies in a Traffic Signal Management 

Plan. 

The following principles provide the basis for an agency to develop an objective-based traffic 

signal management program: 

1. Clarity of objectives. 

2. Attainable performance evaluation linked to those objectives. 

3. Standards of performance (intended, for example, to score well on the Signal Timing 

Report Card) based on objectives rather than agency activities, especially arbitrary 

frequency of activities. 

4. Resource requirements based on objectives rather than industry norms. 

5. Clear and consistent communication with policy makers and elected officials. 

6. Systems engineering in thought rather than merely in deed. 

These strategies are discussed in the sections that follow. 

Clarity of Objectives 

As previously described, a good basic service concept is based on a simply stated objective. 

Drivers have simple overall expectations: 

I want to drive to my destination at my desired speed with the minimum of attention. In the 

absence of achieving that goal, I want to be treated fairly and predictably so that I can plan my 

day with the minimum of uncertainty. 

This leads to a simple objective for agencies to articulate: 

We will do our best to avoid making drivers stop, but when we must make them stop, we 

will delay them as little as possible, within the context of safe operation.

As previously described, these objectives lead to a few high-level strategies for the agency to 

promote, including: 

 Field infrastructure reliability. 

 Signal timing that minimizes and balances congestion. 

 Signal timing that promotes smooth flow. This objective is an amalgamation of more 

narrowly cast objectives, such as delay, stops, and so on, but those objectives are 

evaluated in light of the broader objective of smooth flow. 

 Signal operation that corresponds to conditions predictably and consistently. 
 

 Versatile signal timing that provides broad-banded solutions rather than being narrowly 

optimized for a specific condition. (See Appendix 1 for further discussion.) 

Attainable Performance Measures and Standards of Performance 

If the strategies listed above are relevant to achieving the goal of fulfilling motorist expectations, 

the performance measures should be related to those strategies. The interviews revealed that 

even the best agencies find it difficult to measure their performance (other than in terms of 

citizen complaint calls) and stay focused on their objectives. Too often, agencies focus on traffic 

performance objectives such as delay and stops that are based on aggregate measures that are 

not directly perceivable by motorists, and too often the achievement of good maintenance is 

hidden by the effects of traffic growth with respect to network capacity outside the control of 

traffic signal operations staff. 

Thus, an effective operational plan will define how the agency has implemented and measured 

the progress of those strategies. 

Field Infrastructure Reliability. 

The broadest measure of the reliability of the traffic infrastructure is: 

The percentage of time motorists see what traffic agencies intend for them to see.

There are two general approaches for accomplishing this objective that emerge from the 

discussion of agency archetypes: By design and by maintenance response. Maintenance 

response includes emergency and preventive maintenance, and agencies have difficulty 

establishing the latter based on their resources being consumed by the former. 

Agencies that have successfully implemented preventive maintenance programs have often 

built new programs, with new technicians and new equipment, based on clear productivity 

objectives. For example, the City of Austin, Texas established a preventive maintenance 

program in the mid-1980's that resulted in the addition of two technicians, each with a small 

service van equipped with a short telescopic bucket. These technicians were entirely devoted to 

preventive maintenance, as a program for which funding was sought separately and distinctively 

by the agency staff from the local policy makers and elected officials. The program was based 

on the principle that the agency would not have to expand its maintenance force in future years 

to keep up with additional demand for emergency maintenance because of the effects of 

preventive maintenance. 

Agency staff measured and reported the effectiveness of that program in terms directly linked to 

the objective of the program: How many traffic signals received preventive maintenance during 

the year? A performance expectation for the technicians was established at four intersections 

per shift for preventive maintenance, and the technicians worked a night shift to avoid 

congested periods. What the agency did not do was close the loop to analyze whether average 

emergency maintenance declined as a result of improved preventive maintenance, and as a 

result lost focus on the program after several years and folded the new technicians into the 

regular technician pool. As with the Report Card, performing the activity alone is not enough. 

With maintained focus, the agency would likely have been able to report a decrease in the 

number and severity of emergency maintenance calls. 

The same is true on the system side for coordinated systems. In order to increase the 

percentage of time the motorists see what the agency intends them to see, the operation must 

actually be observed. The interviews revealed that agencies did not observe the operation of 

their signal systems routinely to make sure they were running as intended. To some extent, this 
 

forms one of the fundamental purposes of a traffic signal system, which is to monitor the local 

infrastructure and report faults when they occur. Thus, the need for field observation can be 

minimized by a design solution rather than by merely increasing the maintenance 

function. But requirements leading to such design must be clearly articulated. 

Signal Timing 

Measuring traffic performance can be related to two very different questions: 

1. Has the signal operation degraded to the point where it needs to be revised? 

2. Is the signal operation good? 

The first question has usually been the result of an arbitrary time limit, and the Report Card 

evaluates effectiveness here on the basis of how often an agency revises its signal timings. But 

an activity-based solution is not necessarily an effective use of limited resources. 

In an ongoing project considering this question, one result has been that signal timing designed 

to accommodate heavier traffic (short of congestion) will also accommodate lighter traffic, with 

little impact on travel time. That work defines the solution space for signal timing as ranging 

from nearly no traffic to the point of congestion in a typical day (which may be in the future). 

Considering that agencies usually provide effective signal timing with four or five coordination 

patterns for this comprehensive range of conditions, the research pointed out that trends over 

time could be accommodated by providing signal timing plans designed to cover the solution 

space at the outset. (See the discussion on versatility in Appendix 1.) 

The thornier question is evaluating given signal timings in absolute terms, especially in 

congested networks. The interviews revealed a very simple metric for determining whether 

signal timings seemed reasonable and equitable to motorists: Citizen complaints. Thus, one 

means of measuring improvements in this objective is by summarizing citizen complaint activity. 

Raw numbers are probably not helpful, however, because notice in the press can cause a public 

reaction that would not otherwise have occurred. These anomalies should be measured and 

discounted. Most agencies now track citizen complaints. One of the interviewers, for example, 

reported that all complaints were processed by a central operator at the agency, and tracked to 

ensure that they are resolved timely. A reduction in the number of complaints per signal, or the 

failure of complaints to keep pace with growth, would indicate progress in this area. The 

prevention of a sudden and sustained increase in complaints would indicate that the agency has 

not slipped in this measure. 

By measuring signal timing in this way, agencies can avoid the enormous task of attempting to 

measure traffic performance comprehensively. But for agencies that have the resources, there 

are ways to collect relatively simple performance data using travel time data collection, as 

suggested by some of the archetypes, using a pair of technicians (one for the morning period 

and one for the afternoon period) for each 200 or so arterial systems that are evaluated on an 

annual basis. These technicians can collect peak-period travel time data in half a dozen runs on 

an arterial, from Monday afternoon to Friday morning, keeping track of season-over-season or 

year-over-year trends. 

Objective-Based Resource Allocation 

With a basic service concept based on keeping traffic moving, many of the activities undertaken 

by agencies may be seen as tangential to their objectives. In developing a traffic signal 

management plan, each agency should consider how each activity actually contributes to 

achieving their objectives. A commitment to the operation on the street was reported as critical 
 

during the interviews, and the agency archetypes most committed to street performance can be 

seen to achieve the best results. 

For example, an operations plan should include a description of how the agency will monitor 

signal operation to make sure it is operating as designed, and a description of how the agency 

will observe that traffic flow is still being accommodated. For agencies with severely limited 

resources, simple observation may be the only choice, but even that is often undone even by 

agencies that don't face such severe limitations. While agencies usually monitor their response 

to citizen complaints, they should also provide a mechanism for responding to complaints 

generated by their own staff. For example, the City of San Antonio published time-space 

diagrams for all coordinated arterial streets in a notebook, and provided those (with training in 

their use) to all traffic-department employees who spend their day on the street. Their 

instructions were to pay attention to flow anomalies, such as unexpected queuing or unexpected 

repeated stops. This is one simple and inexpensive mechanism for monitoring system 

operation. Approaches like this are particularly useful for state agencies that have widely 

dispersed small-scale systems that often don't provide communication to the traffic operations 

office. 

The operations plan should also include a description of the mechanism by which these 

observations are followed up with review by operations staff. It is not the recommendation to 

impose a cumbersome tracking program, but observations from staff should be afforded at least 

as much accountability as citizen complaints, and this is often not the case. 

The focus of the operations plan should be on results, not on activities. A system that provides 

skilled qualitative review of every coordinated system in the jurisdiction of the agency every year 

is preferable to a system that provides, say, microsimulation of only a few systems receiving 

public or political attention. The difference between these is the same as the difference between 

preventive and emergency maintenance. The resource-intensive analysis methods, including 

those that require detailed data collection and analysis, should be reserved for problems that 

cannot be solved by simple skilled observation. 

But agencies should also include in their operations plan a commitment to the basic design of 

the signal timing for the system. A series of qualitative revisions to operation may be 

counterproductive if it undermines the basic operational concept. For example, a series of signal 

timing adjustments may ruin progression without the technician making the adjustment realizing 

it. All such adjustments should be vetted in light of the original intent of the operation, and if an 

adjustment is needed that can't be accommodated within that original concept, the agency 

should consider developing new timings. 

Many such approaches are possible, but the important recommendation is that agencies don't 

ignore the responsibility to allocate resources based on operational objectives rather than 

merely on activities. 

Clear Communication Up the Line 

Most traffic signal practitioners prefer to work anonymously within their agencies. This attitude is 

a natural outgrowth of the negative experiences that often accompany such interaction. In many 

agencies, traffic signal staff are precluded from direct contact with elected officials, and 

frequently are put between the rock of citizen complaints and the hard place of agency upper 

management and public-relations staff that are incentivized to please politicians. This 

uncomfortable position often leads to a cynicism that can undermine the effectiveness of the 

agency more deeply than any budget shortfall. One common outcome is that responding to 

citizen complaints and requests for information from elected officials is often delegated to non-
 

professional staff who are technically skilled but perhaps not able present the information 

consistently with agency goals and strategies. 

An operations plan should include the description of a mechanism by which the progress of 

programs, including routine operational programs, is reported to agency management, policy 

makers, elected officials, and the public. The mechanism should allow both ad hoc and 

systematic reporting, and all the reporting should be based on operational objectives rather than 

on agency convenience. 

These communications need not be excessively formal or highly produced. The City of 

Arlington, Texas developed a means of communicating to management in the form of a 

technical memorandum called an "Informal Report to Mayor and City Council." These should be 

short and descriptive, rigorously factual, and closely related to the interests of the motoring 

public. One of them, for example, reported on the results of an agency-wide signal retiming 

effort conducted to update timings five years after a signal system had been installed. As with all 

the informal reports, the organization of the report included a background, discussion, and 

conclusion. Improvements were based on actual measurement of travel times, using a floating 

car method. Analysis related these travel times to average speed, stops, delay, and emissions, 

but travel times received top billing. The report provided only a summary of the entire network, 

and was less than two pages. During each year, the agency developed dozens of these reports, 

and they were the basis for winning the ITE Urban Traffic Engineering Achievement Award. 

The City of San Antonio was more limited in resources by far, but still established basic 

principles for communicating outside the operations staff. These were: 

1. The story told to citizens is the most important story in the agency. If it is ineffective in 

achieving citizen support and satisfaction, it will also not achieve policy and political 

satisfaction. Consistent with this importance, all citizen complaints concerning signal 

operation were not delegated, but handled directly by the professional in charge of the 

program. This had the dual benefit of telling the story most effectively, and making sure 

that the creator of the policy learned how to express it most effectively. 

2. Requests for information from top management and elected officials must be responded 

to meaningfully within seven calendar days. This included those requests that required 

data collection, such as signal warrant studies. 

3. Information presented to upper management would be presented with a high standard of 

professionalism, empowering and enabling those upper managers to represent that 

information to policy makers and elected officials more effectively. For example, the 

before-and-after travel-time studies associated with new traffic signal timings were 

summarized in a professionally produced report that extended the memorandum 

concept mentioned above to a report that could be distributed to the public. 

An operations plan should include principles for communicating outside the agency, with special 

emphasis given to reporting successful completion of routine and special projects, and to 

making it the direct responsibility of the person in charge of the program to articulate it to the 

public. Those principles should be directly related to the objectives of the program. For example, 

a new signal system might be built to improve the management of field infrastructure, in which 

case the report should be related to that objective, e.g. the number of citizen complaints that 

were responded to without a field visit because of the system, the number of faults that were 

discovered and corrected before the public complained, the increased number of intersections 

updated with new and improved timings as a result of more efficient database management, 

and so on. Signal timing projects, on the other hand, should show the benefits of new timings in 
 

terms most relevant to motorists: Minimize travel time and travel time unreliability, which is 

usually interpreted as unpredictable and inequitable operation by motorists. 

Meaningful Systems Engineering 

An operations plan should include a requirement that all projects follow a meaningful systems 

engineering approach. This requirement should apply to all activities defined as projects, with an 

objective, a strategy, a tactical implementation, and a result. 

This is particularly true for the replacement of signal systems, which are the most expensive and 

perceived to be the least successful of traffic signal management projects. 

Most signal systems are justified based on traffic performance and safety. Yet these 

improvements result from signal timing improvements, not signal systems, and can be achieved 

through such approaches as time-based coordination.

Most agencies contemplating a signal system, however, have real needs not served by timebased coordination. Those needs can be summarized simply: Manage field infrastructure. 

Systems engineering is a process by which real needs are identified first, and then the project is 

formulated and tested to confirm that those needs are addressed. As an established branch of 

systems development, systems engineering is well documented in wide-ranging literature (in 

addition to being a requirement for Federally funded projects, see here: 

http://www.ops.fhwa.dot.gov/int_its_deployment/sys_eng.htm) and generally follows this 

process: 

 Document what the agency does using the proposed system. (This is not what the 

system does, which will be developed later, but what the people do that the system must 

support. As such, it doesn't describe the system at all; it describes the agency.) These 

activities are then broken down into a list of needs, called user needs. The 

documentation of this step is called a Concept of Operations.

 For each need, define a requirement or series of requirements that the system must 

fulfill in order to address that need. These requirements form the Requirements 

Document and show explicitly how the requirements trace back, point by point, to the 

user needs. 

 Design the system such that all the requirements are fulfilled. This is the first step where 

the design of the system is contemplated, and this is the first description of the system 

itself. The design includes the normal technology analysis, design documents, and 

ultimately plans and specifications. Every design feature must be justified by playing a 

role in fulfilling at least one requirement, and every requirement must be fulfilled. One of 

the design documents is the Requirements Traceability Matrix, which explicitly 

documents how the design fulfills the requirements. 

 Test system components against the design. This is called Verification.

 Test the system's ability to support the activities defined in the Concept of Operations.

This is called Validation.

With that outline, a signal system project Concept of Operations will include a plain description 

of what operations staff will do. For example, when a citizen calls the practitioner with a 

complaint about the operation of a signal, the practitioner needs to be able to observe the 

operation of that signal in real time to evaluate the complaint. Many causes of the complaint can 

be observed by watching the signal operate through the system. Thus, the agency’s activity is to 
 

respond to a citizen complaint by first observing the operation of the signal in real time, checking 

that: 

• The signal is not on conflict flash 

• The signal is in coordination 

• The pattern is correct 

• The controller time of day is correct 

• The timing has not been modified 

• The detectors are cycling normally 

• The signal is cycling normally 

Further, the practitioner may benefit from seeing the traffic demand at the intersection using 

some form of traffic monitoring. 

Based on what the observation reveals, the practitioner may dismiss the complaint, determine 

that a malfunction has occurred and refer it to maintenance technicians (or repair it through the 

system), or determine that the signal timing needs closer observation for possible revision. 

The forgoing description of the agency’s activity is the critical basis for determining the need for 

a traffic signal system. They provide a clear basis for requirements that will be used to evaluate 

the design of the system, such as the requirement to provide a real-time display, the 

requirement to include detector actuations in that display, the requirement to build a 

communications network that can keep up with that real-time display, and so on. Those 

activities should therefore be the subject of a proper Concept of Operations. The requirement, 

for example, that the system software include a real-time display can be traced directly back to 

this activity. 

Most agency-developed systems engineering approaches focus on the system at the outset, 

rather than on the activities of the agency, with the result that the system eventually does not 

fully support those activities, and the project fails to meet expectations. This is especially true if 

the system was sold to policy makers on the basis of traffic improvements, which may be 

elusive, especially if traffic demand is increasing fast enough to mask any resulting 

improvements in signal timings. 

Some agencies now require a business-plan approach for all their activities, and the systems 

engineering documentation will provide the necessary rigor to describe those activities, their 

objectives, and how those objectives will be measured. 

Meaningful systems engineering is crucial to incorporating new technologies, as the above 

examples illustrate. An operations plan should provide an outline for a systems engineering 

process to be implemented for each routine and special project undertaken by the agency, 

following established approaches. These steps need not be excessively complicated. For 

example, many projects undertaken to support a particular activity might be described in a page 

or two. Even routine system projects can use a model concept of operations developed by the 

agency or within the industry, keying on the activities needed by that agency. 
 

Sample Outline for a Traffic Signal Management Plan 

Chapter 1. Objectives and Requirements. 

In this chapter, define in concrete terms the operational objectives of the agency. While the 

definition should be concrete, it does not have to be specific. For example: 

We will do our best to avoid making drivers stop, but when we must make them stop, we 

will delay them as little as possible, within the context of safe operation.

This mission statement is not specific, but it is concrete, and it can be used as the basis for 

establishing high-level requirements for the agency. Other objectives are possible, given local 

priorities, and based on the expectations of motorists in the region. The objective should avoid, 

however, specific performance standards, because traffic signals do not create capacity, and 

any given performance standard will fail when demand exceeds capacity. 

Based on the objectives, the agency should establish high-level requirements that lead to 

strategies implemented by the agency. These strategies must be linked to the objective.These 

requirements may include: 

 Reliability standards, based on the percentage of time the motorists see what the 

agency intends for them to see. 

 Signal timing standards including: 

o Minimizing congestion and managing unavoidable queuing. 

o Promoting smooth flow 

o Appropriate for conditions 

o Versatile to provide acceptable operation across the range of conditions 

Note that these requirements do not impose either a particular design or even a given level of 

resources. In the face of limited resources, creative design may fulfill these requirements, as 

described throughout this report. Some examples: 

 Improving reliability by improving design and initial construction quality, by minimizing 

the dependence on features and infrastructure (particularly detection) and by using 

system approaches that do not depend on fragile communications infrastructure. 

 Improving versatility by designing signal timings that are purposely broad-banded, such 

as progression-based solutions, rather than narrowly optimal as might be suggested by 

some optimization programs. Or, alternatively, strongly funded agencies might fulfill this 

requirement by implementing systems that continuously respond to changing traffic 

conditions based on measured inputs. Both of these fulfill this high-level requirement, but 

they do not both make the same resource demands. 

This chapter does not need to include these strategies, but should establish the standard by 

which these strategies will be evaluated. These standards become the agency's definition of 

good, basic service. 
 

Chapter 2. Responsiveness to Citizens, Media, Policy Makers, and Elected 

Officials 

This chapter should lay out the standards defining the agency's responsiveness to motorists 

and other users of traffic signals. Examples of these standards include: 

 All citizen complaints will be responded to in kind. Telephone complaints will receive a 

telephone response, written complaints a written response, and so on. 

 All citizen complaints will be recorded by the person receiving the call, and responded to 

within a certain time period to be determined by the agency. 

 All complaints should be checked to rule out malfunctions first. This strategy provides a 

range of requirements for signal systems and their ability to provide fault and real-time 

monitoring. 

 Operational complaints that are not malfunctions should be addressed by the person 

who is responsible for the design. Explaining a design should never be delegated. 

 All requests requiring data collection and studies should be addressed within a given 

time period defined by the agency. 

 All complaints and requests should be tracked. The complexity of the tracking method is 

a strategy unique to each agency, but at the very least, the tracking method should 

ensure and be able to demonstrate that all complaints and requests are completely and 

expeditiously addressed. Most agencies already track requests coming from policy 

makers and elected officials, but the agency should also find ways to track common 

citizen complaints. 

 The agency should define how the traffic signal operations staff should or should not 

communicate with the media. Many agencies already have such policies in place, but 

within what is allowed by those policies, agencies should ensure that the highest priority 

is given to the story told to the public. That usually means providing the agency's most 

articulate, positive, and knowledgeable explainer to respond to media requests. 

 The agency should define standards for communicating program and project results to 

policy makers, elected officials, and the public. Those standards should include the 

format for such communications, an explanation of the objective of the program or 

project, the approach taken to achieve the objective, and the results in terms relevant to 

the objective. Agencies should describe here which programs and projects will be 

communicated this way, but it should at least include all programs and projects that 

receive specific funding, either within the budget or from outside sources. 

Chapter 3. Maintenance Strategies to Achieve Objectives 

This is where the agency lays out its maintenance approach. This chapter should include a clear 

explanation of how the agency will respond to limitations and constraints in maintenance 

resources, including limitations in staff numbers, training levels, and equipment. These 

strategies may include, for example, how an operational approach that does not depend on 

extensive detection minimizes the need for a large and difficult to maintain detection 

infrastructure. They should include how consistent design standards will be used to prevent substandard installations that require high maintenance levels. They should include how the use of 

features and technology within the signal equipment will be kept within the knowledge, skills, 

and abilities that can be expected for the job descriptions and remuneration for maintenance 

technicians. 
 

Chapter 4. Operations Strategies to Achieve Objectives 

In this chapter, the agency will describe the following: 

 The operational approach. Examples include maximizing progression, eliminating onset 

of yellow during platoon arrivals, pedestrian accommodation, clearance interval 

approach, basic detection strategy (consistent with the agency's resources), signalized 

left turn warrants, allowable phase sequence approaches, and so on. 

 Evaluation. How will the agency ensure that the operation on the street meets 

objectives, including operating according to design, providing smooth flow, providing 

sufficient versatility, and so on. The evaluation approaches can be quantitative (e.g. 

travel-time studies) or qualitative (field observation), but they must be directly linked to 

the objective. If the objective is to keep traffic moving, then the evaluation must assess 

how well traffic moves. If the objective is to maximize throughput through a bottleneck, 

then the evaluation should measure throughput. If the objective is to manage queuing at 

a bottleneck, then the evaluation should directly evaluate queuing. If the objective is to 

improve safety at a location, then the evaluation should include tracking crashes. 

Chapter 5. Design Strategies to Achieve Objectives 

Most agencies already have documents guiding infrastructure design requirements. But those 

documents do not usually set quality standards as they affect operations and maintenance, and 

this chapter provides an opportunity for agencies to do so. This section should apply consistent 

standards for traffic signal design, including street furniture, pedestrian accommodation, 

numbers and placement of signal heads, and so on. Not all agency operations staff are 

responsible for these design standards, in which case they should be written down here with an 

analysis of how the standard does or does not impose limitations on operations and 

maintenance. This provides the operations practitioner with an understanding of how design 

affects operations. 

A most important section in this chapter concerns the implementation of automated systems, 

either for traffic signal operation or for management (including, for example, a citizen complaint 

tracking system). This chapter should lay out a meaningful systems engineering approach, 

including how each project (internal or external) will progress from a clear statement of needs 

through a demonstration of how the finished project supports those needs. The process should 

include at least the following steps: 

 The Concept of Operations, including how an agency will use the system. The agency 

should write this document internally, or be the primary audience for a document written 

by consultants. In all cases, it should focus on what they will do, not on what features 

they want. 

 Requirements. Each activity described in the Concept of Operations imposes one or 

more requirements. For example, an activity that includes an operator reviewing the realtime operation of the system leads to requirements that establish that real-time 

capability, and a display capability that shows the operator what they need to see to 

complete that activity. Those requirements become the standard for design. 

 Verification. In this step, the designer demonstrates how each element of the design 

fulfills the requirements. This term also describes how the system will be tested to prove 

that it conforms to the design. 

 Validation. Here the implementer demonstrates that the system indeed supports the 

activities described in the Concept of Operations. 
 

Appendix 1. Signal Timing Versatility Concepts 

Versatility is one of the more critical points in objectives for signal timing programs, but it 

receives little attention or consideration by many practitioners. The typical current approach to 

performing signal timing is as follows: 

1. Collect physical intersection and network data and enter into signal timing optimization 

software 

2. Collect 15-minute turning-movement counts at all intersections 

3. Collect road-tube counts at all intersections 

4. Review data to determine when traffic patterns change significantly, with "significantly" 

being defined to fit a pre-determined number of signal timing plans 

5. Select a representative 15-minute period for each period of unique traffic pattern 

6. Convert the 15-minute volumes to hourly volumes, and enter them into signal timing 

optimization software 

7. Review the output of the optimization software and make adjustments, usually using a 

time-space diagram to represent the coordination pattern 

8. Implement the timings on the ground 

9. Fine-tune the timings on the basis of field observation 

Several of these steps are quite expensive, particularly including the collection of 15-minute 

turning-movement counts at all intersections. This data-driven process implies that traffic 

volumes are more important than traffic performance, given the resources required to collect 

them. A key weakness of this approach is that volume data is of limited value to the practitioner, 

and often too expensive to collect routinely. 

Practitioners use volumes primarily because optimization software requires it. And the software 

requires it because we have no easy means of directly measuring what is really important, and 

that is whether the timings are serving the representative desires of the users of the network. 

These desires represent aspects of the overall motorist objective for smooth, predictable flow, 

and we characterize them generally based on some combination of the following objective 

functions: 

• Minimize delay 

• Minimize stops 

• Minimize fuel consumption 

• Minimize emissions 

• Maximize progression 

• Maximize throughput 

• Manage queues 

• Minimize travel time (or travel time unreliability) 
 

• Maximize right-of-way for non-automotive travelers, including pedestrians, bicycles, and 

transit riders 

Modeling these objectives, especially considering that all the objectives are important at some 

level in all situations, is difficult even for microscopic simulation software. Most signal 

optimization software chooses some simple combination of a few of these objectives, and even 

these are quantified by simplistic models. The models themselves have been designed to use 

the only traffic data that is readily available, and that is traffic volume. 

The traditional approach therefore starts with an expensive data collection process, which is 

required by a simplistic model that considers too few objectives, to produce signal timings 

optimized for a single 15-minute period which may or may not be usefully representative of 

other periods, especially over the coming months and years. 

Skilled practitioners usually then are compelled to spend considerable time making field 

adjustments of the resulting timings, based on their experience-driven and implicit 

understanding of meeting the needs and expectations of as many of their users as possible. 

This process is also resource-intensive, and not all agencies have access to such skills. 

Finally, the data on which the system is designed changes constantly. Timings narrowly 

optimized for several 15-minute periods may not provide the versatility needed to remain 

reasonably close to an optimum throughout any given day, or over time as daily, weekly, 

seasonal, and long-term trends affect demand. This leads to the usual recommendation to 

perform the above process again in an arbitrarily short time, such as every two years. 

Tools are not available to evaluate signal operation on the basis of better-defined objectives and 

optimization processes that use measured performance rather than modeled performance. 

Rather than the typical steps listed above, a better approach that is more sensitive to available 

resources and more versatile, might be the following: 

1. Identify intersections where minor movements are controlled by non-vehicular factors. 

There is no need to collect data if the minor movement green time will be controlled by 

pedestrian crossing times, or if the traffic is obviously so light that any reasonable 

minimum green will serve it. In many cases, timings on these approaches can be set 

arbitrarily, with local actuation shortening the green time as allowed by demand. 

2. Collect turning movements only at intersections where minor movement green times 

cannot be estimated. 

3. Identify network topology, primarily the spacing between signals and the prevailing 

speed of traffic. 

4. Choose the range of cycles lengths, based on coordination timings that resonate 

between signal spacing and prevailing speed. 

5. Choose offsets (and, where desired, phase sequence), based on progression and 

directional split, for a comprehensive variety of directional splits. Directional splits rarely 

exceed 70% in the peak direction, and five plans should be sufficient to represent all 

directional splits from 70% inbound to 70% outbound on the most extreme arterial street. 

Most streets would need only three levels of directional bias. 

6. Determine green splits at intersections where minor movements are not dictated by nonvehicular factors. First, identify the directional splits in the turning-movement data (by 
 

inspection), and choose 15-minute periods within those directional split periods to 

characterize minor-movement demand. Then, determine green times equitably. 

7. Implement and fine-tune. 

Because the cycle length, offset, phase sequence, and main-street green time are largely 

determined by the geometry of the network, using volume-based optimization tools often has 

little additional to offer. Finding an appropriate progression solution may be difficult in more 

complicated networks, but even "guess" volumes can often find those solutions as accurately as 

measured volumes, especially considering the potential inaccuracy of those measurements. 

Often, optimization processes work to levels of precision far in excess of needed or supported 

accuracy, which is an error most engineers are trained to avoid. 

The figure below represents the concept of versatility. 

Good operation is represented by the peaks in the solution terrain, and good operation can be 

maintained by jumping from peak to peak. The current methods used by many agencies 

attempts to identify a few peaks to broadly represent the terrain, rather than to start with the 

whole solution terrain and represent it with versatile timing patterns. Using this approach, the 

most complicated arterial street may be timed with a dozen plans, none of which requires data 

at most intersections and only a few of which require significant data or design resources. Most 

typical arterials would need less than half that many plans, especially if the signal timings are 

designed for versatility. 

Such an approach would provide good basic operation, saving expert resources for those 

conditions and geometries that demand more effort, such as congested conditions. 

It should be pointed out that a versatile set of signal timing plans designed to broadly 

accommodate the solution terrain can support the implementation of traffic-responsive operation 

far more easily, and are also much more resistant to degradation over time. 
Improving Traffic Signal Management and Operations: 

A Basic Service Model 

U.S. Department of Transportation 

Federal Highway Administration 

Office of Operations 

1200 New Jersey Ave., SE 

Washington, DC 20590 

Toll-Free "Help Line" 866-367-7487 

FHWA-HOP-09-055