1. Guidance for Operations and Maintenance Objectives and Performance Measures
The objective of this section is to provide a guideline to assist managers and practitioners to prioritize the operations and maintenance objectives and performance measures to evaluate staffing and resource needs required to effectively operate and maintain traffic signal systems. Ineffective operation and maintenance of traffic signals may have safety implications and contributes annually to millions of hours of unnecessary traffic delays, congestion, fuel consumption and air pollution. The issues associated with understaffing and under funding traffic signal system operation and maintenance, activities are indigenous to urban, suburban and rural areas.
Major contributors to the inconsistency found in traffic signal operations and maintenance budgets include:
- A lack of clear guidelines describing traffic signal operations and maintenance activities and the resources required to support these activities;
- The lack of documented objectives and performance standards;
- Funding mechanisms that are geared more towards project development than operations and maintenance.
Some effort has been made to provide a benchmark for, and to promote good traffic signal operations and maintenance practices through the National Traffic Signal Report Card and associated self-assessment survey. These efforts have been supplemented through traffic signal operations audits and traffic signal operations reviews conducted by the FHWA. In 2005, the National Traffic Operations Coalition (NTOC) assigned a national grade of D- to traffic signal operations and maintenance practices. In 2007, the National Traffic Signal Report Card (5) grade improved slightly to a grade of D. The agencies that improved their scores employed "more effective management techniques and are taking a more thoughtful approach to resource allocation." (6)
While the Traffic Signal Report Card evaluates conformance to what is considered "good practice" it does not define traffic signal operations or maintenance. Clearly defining traffic signal operations and maintenance are essential to beginning the discussion about staffing and resource needs to support these functions. The following working definitions are offered for traffic signal operations and maintenance as a result of surveys conducted by the FHWA Resource Center and a glossary of terms developed by the Transportation Research Board Regional Transportation Systems Management and Operations Committee.
Traffic signal operations is the active prioritization of objectives and active collection of information to efficiently manage traffic signal infrastructure and control devices to maximize safety and throughput while minimizing delays.
Traffic signal maintenance includes the preventative and responsive activities to preserve traffic signal infrastructure and control devices necessary for the safe and efficient utilization of arterial, collector and local roadways.
Under a given set of geometric conditions, and without budgetary, technological and knowledge constraints the expectation of a minimum delay or ideal traffic signal system might be achievable. The goal of achieving an ideal traffic signal system, while unachievable given current constraints, should nonetheless represent the desired level of traffic system operation. To bring reality to the situation the ideal traffic signal system must be constrained to obtain goals that are Specific, Measurable, Achievable, Realistic and Timely (SMART). This requires clearly asserting objectives that are realistic given the resources available.
Past approaches to development of resource and staffing criteria for operation and maintenance of traffic signals have often provided guidelines in terms of the number traffic signals that can be maintained and operated per number of personnel performing these tasks. These approaches do not adequately consider the how agencies view their role, operations objectives and desired level or needs for traffic signal management operations and maintenance. Responsible agencies differ, in many characteristics. Some of these key variables include:
- Number of signals and changes in number of signals
- Variations in knowledge, skills and abilities of maintenance and engineering personnel.
- Differences in functions that the systems and agencies must perform.
- Organizational structure of the responsible agency (sharing of resources with other functions) and budgeting structures.
- Geographic configuration of traffic flow network i.e. grid, arterial and the overall number and size of other facilities in the transportation network (freeways, interstate, transit, freight, land use etc.)
- Density of traffic signal network relative to population density.
- Congestion levels.
- Type of signal system (e.g. distributed or centrally controlled); distribution of signals on the network and need for interconnection.
- Procurement of maintenance (own forces vs. contract).
- Procurement of signal timing plans (own personnel vs. consultants).
- Institutional issues such as union issues (e.g. union vs. nonunion employees, particularly as they relate to contractors.)
With this large number of variables, and because agencies provide essentially the same types of services in many different ways, it is essential that agencies develop a set of operations and maintenance objectives that are consistent with the agencies traffic management philosophy. The objectives should be SMART and defined in terms of performance, reliability and function (PRF) based criteria (as compared with resource based criteria.)
The following five key elements have been identified to serve as a basis for developing objective based criteria:
- Section 1.2 defines these elements and describes the Objective Oriented Operation (OOO) requirements for these elements. The Management element describes a set of candidate objectives, a subset of which may be adopted by the agency. Section 1.3 provides detailed conclusions and recommendations developed during the study.
1.2 Definition of Objective Oriented Operation (OOO)
Traffic signal operation is one of the transportation industry's most visible services provided to the traveling public. Therefore, it is appropriate that top management and elected leaders be attentive to and supportive of good traffic signal operations. Outlining and documenting a management approach for traffic signal operations is very important. Committing the appropriate resources (staff, funding and attention), coordinating activities, communicating with the traveler and cooperating and integrating with others are all important management activities (5).
Management practices for OOO should include the following:
- Supervision of traffic operations by a PE and/or PTOE.
- Availability of a mission statement and annual review. The mission statement contains a set of agency objectives. A listing of representative objectives from which the agency objectives may be developed is shown in Table 1.1. A set of representative measures is also included in the table. The measures selected by the agency should incorporate the following features:
- The measures should span the traffic system and agency functions required without significant redundancy. Be sufficiently general to encompass the different requirements of all agencies.
- Be measurable or answerable using existing information, information which can be readily obtained or information that may take some effort to collect but which is vital to the determination of the capability of the traffic system relative to the OOO.
- Minimize the need for subjective judgment to accomplish evaluation.
- Collect and analyze data for traffic system measures selected for the mission statement. Management plans should incorporate a documented methodology for this analysis including a recommended time interval for reviews. The time interval should reflect traffic conditions, the type of network and the data collection capability of the traffic system. The interval should not, however, exceed 30 to 36 months. Continuous automatic data collection and subsequent data mining may assist in developing the database for the analysis. These measures primarily serve to identify trends in performance to provide a comparative basis for year-to-year evaluations. Based on these measurements and other requirements, a plan for required physical upgrades of the signal system or changes in the approach to signal timing and phasing should be developed. While many measures may be considered, a limited set that can be readily measured are the most useful. For systems whose mission is to provide basic signal control, a representative set might include:
- Travel time.
- Crash analysis (13,14)
- Intersection level of service.
- Approaches worse than Level of Service F (control delay exceeding 80 seconds per vehicle).
- Development and analysis of traffic system reliability data on an annual basis.
- Availability and annual review of a Concept of Operations. Changes in functional requirements such as the need for preemption, transit priority, diversion timing plans and evacuation signal timing plans should be included in the review.
- Compliance with the Regional ITS Architecture requirements pertaining to traffic systems.
- Availability and annual review of a strategic management plan. The plan should have both long-range and short-range components. It should provide for the review and updating of the traffic system plant, engineering, operating and maintenance personnel requirements and purchased services. It should review the design, operations, maintenance and training items described below. The review should be approved by the director of the operating agency. The management plan should be shared with employees.
- Capability should be available for easy communication with the motorist. Examples include a well-publicized telephone call-in capability and an email response capability on the agency's web site.
- Regional traffic signal operations should be established to ensure that timing plans are coordinated with those of neighboring agencies. The management approach should also consider coordination with neighboring agencies to respond to incidents and to both planned and unplanned events.
Table 1.1 Examples of Objectives and Measures for Traffic Signal Systems
|Mechanism To Achieve Objective
|Possible Measurement Technique
|MOBILITY, FUEL CONSUMPTION AND EMISSIONS
|1. Reduce delay and fuel consumption for normal traffic
patterns. Signal retiming should improve delay and fuel consumption by
a specific minimum amount each time retiming is performed.
- Improved signal timing.
- Improved level of traffic system control (e.g traffic responsive,
- Real time adjustment of timing by operator.
- Improved maintenance response time.
- Vehicle hours delay.
- Gallons fuel reduced.
- Monitoring and tracking of citizen complaints, (provide regional
311 or equivalent phone number for reporting)
- Travel Time & delay runs.
- raffic system data.
- Simulation (e.g. Corsim) independent of signal timing programs.
Use of traffic system data for input
- Real time performance monitoring
|2. Reduce delay and fuel consumption for incident conditions
and special events. New signal timing plans to support these functions
should improve delay and fuel consumption by a minimum of 2% when these
plans are in effect.
- Signal timing – items a, b, c in 1 above.
- Support of incident management using CCTV and other information.
- Same as 1.
- Same as 1.
- Simulation with reduction in incident clearance time.
|3. Reduce emissions.
|Same as 1.
|Kg of CO, NOX, SO2, CO2.
|Derive from gallons saved.
|4. Reduce crashes resulting from left turns, red-light running
and signal outages. Improvement measures should result in a 1% reduction
|Improved maintenance response time. Implementation of countermeasures
to reduce crashes due to left-turns and red-light running (13,14).
|Analysis inference techniques using response time maintenance records.
|5. Reduce secondary crashes resulting from incidents. Improvement
measures should result in a 2% reduction in secondary accidents.
|Support of incident management using CCTV and other information.
|Secondary crashes reduced
|Analysis inference techniques using reduction in incident clearance
|COMMUNICATION WITH PUBLIC AND PUBLIC PERCEPTION
|6. Improved public perception of signal and management center
operations by 1% per year.
- Achieve other objectives.
- Regular reporting to public
- Monitoring and tracking of citizens complaints (provide regional
311 or equivalent phone number for reporting)Develop and provide outreach
material describing how traffic signals function and the benefits
of active operations.Develop website to disseminate information and
reports, provide an online feedback and complaint database.
- Rating scale.
- Rating scale.
- Number of calls, complaints
- Monitor number of calls, time to respond to calls and outcome of
|7. Provide traffic information to public and private traffic
information services. Improved information quality and delivery by 1%
|Make traffic, construction, special event, incident, weather data and
CCTV signals available to traffic services, media, web sites.
|8. Serve as a diversion route for corridor operations. Goal
established by stakeholders.
|b and c in 1 above plus availability of diversion timing plans.
|Same as 1 and 3.
|9. Provide preemption for emergency vehicles and railroads.
Goal established by stakeholders.
|Preemption equipment.. Use of equipment must be carefully restricted
so as not to cause unreasonable delay to general traffic
|Number of critical mission emergency vehicles provided preemption.
|Some preemption systems provide logs of preemptions granted.
|10. Provide transit priority. Goal established by stakeholders.
|Priority equipment used for late vehicles.
|Traveler hours reduced. Variation in delay reduced
|Transit records coupled with simulation with delay and delay variation
|11. Support emergency evacuations. Goal established by stakeholders.
|Evacuation signal timing, phasing, and lane use plans.
|Availability of plans.
|12. Data for planning and evaluation.
|Mining of detector data
|Employment of data by agency or MPO.
|13. Improve internal efficiency of department operations.
|Plans and procedures, training, concept of operations and operations
|Development of review processes to consider traffic signal operations
and maintenance from planning to design and construction.
|Time to implement new timing plans.
B. Signal Timing Design
Traffic signal coordination is one of the most important aspects of good traffic signal operation on arterials. Signal coordination ensures that motorists are able to travel through multiple intersections at a prescribed speed without stopping or with an absolute minimum of stops (5).
Regardless of whether an individual signalized intersection is coordinated with other nearby signals or operates totally independently, there are issues that are critical to how well that intersection operates and serves the public. Reviewing and updating the intersection-specific timing and operational aspects of individual signalized intersections on a regular basis is extremely important, especially where changes in traffic volumes and/or adjacent land uses have occurred since the last review. The issues include reviewing and updating the phasing sequence, detectors, displays, timing parameters and other related operational aspects of individual signalized intersections within a jurisdiction (5).
Signal timing design practices should include the following:
- Review of intersection performance data every three years to determine whether geometric improvements can remedy approaches exceeding 90% saturation for 200 hours per year on weekdays and 100 hours per year at other times.
- Review of intersection performance data for phasing and type of signal control (actuation, etc.)
- Review of signal timing performance using a documented methodology should
be performed at periods established by management plans but should
not exceed 30 to 36 month periods to identify the need for retiming
(see Appendix C).1 Where automatically collected data is available,
it should be reviewed at 6 month intervals to determine the need for
more rapid retiming. A methodology to establish the priority of retiming
requirements should be used (for example see Appendix D).
- Retiming of signals should be performed as part of this review cycle. Data should be collected as necessary to support the retiming process. Timing plan updates should be performed using an accepted methodology such as SYNCHRO, TRANSYT 7F, etc. Retiming should be completed and checked in the field within 3 months of identifying the need for retiming.
- Retiming should be supervised by a PE/PTOE.
- A methodology for determining the number of daily timing plans required as well as weekend and special function timing plans should be utilized. Factors such as saturated approaches, spillback from intersections and turning bays should be given special attention. Strategies that facilitate flow during light traffic periods should likewise be given attention.
Agencies should support operational practices that have been shown in the past to be effective.
Operations should include the following:
- Supervision of traffic operations by a PE and/or PTOE. Supervision should include periodic review and assessment of continuing operations and counseling employees on improving operations. Other supervisory monitoring activities include periodic review of automatically collected data and physical observation of traffic operations.
- The data collected in Signal Timing Design Items B.3 and B.4 should be reviewed to develop a plan for required physical upgrades of the signal system. System upgrades should be accomplished in accordance with the Strategic Management Plan (Item A.7.)
- A plan for remedying reliability deficiencies identified in item A.4 should be developed. Correction of major deficiencies not requiring major capital expenditures should be performed within three months.
- Changes in functional requirements such as the need for pedestrian treatment, preemption, transit priority, diversion timing plans and evacuation timing plans should be identified and a plan developed for their implementation.
- Commitment to continuing education for the professional staff.
- Traffic systems in urban or suburban areas that are of a medium size or larger should provide a capability to monitor real time field information at a central facility for the majority of signals. Manual monitoring should, as a minimum, be provided during weekday peak periods and at such additional times as conditions may require. Smaller systems should be periodically monitored during these periods. Monitoring should include equipment failures and unusual congestion conditions. The operator should select alternate signal timing plans when conditions such as incidents or special operations require. A criterion and process should be employed to establish appropriate monitoring periods.
Maintenance practices should include the following:
- Response time – Response time depends on two factors - time to obtain an indication of failure and time to respond after receiving an indication of failure. The following requirements apply:
- Time to obtain indication of failure - Since closed loop systems and other centrally monitored systems provide an indication of controller failure, rapid failure identification can be accomplished using such techniques if these systems are supervised. Criteria for the percentage of failures that are initially detected within the traffic agency (as compared to reports from police, other agencies or citizens) are:
- For systems in excess of 400 intersections 70% of failures should be detected by the operating agency. In a dense network of coordinated signals, critical failure detection by the agency should approach 100%.
- For systems with 400 intersections or fewer, 50% of failures should be detected by the operating agency. Detection should be considerably higher for a dense network
- Time to respond after receiving an indication of controller or signal failure.
- Within one hour during business hours.
- Within two hours during non-business hours.
The Traffic Signal Report Cards indicate that a significant number of agencies conform to this requirement.
A procedure to identify the level of criticality for the intersection with respect to safety and congestion should be developed. Response priorities should be developed in accordance with this procedure.
- Rates of critical failures (e.g. controller failures, deficient cabinet or signal wiring, short circuits, lightning strikes, etc.) should not exceed F failures per year per for each intersection. Where this rate is exceeded for a period of one year, an investigation to determine the root cause should be conducted. To establish the value of F, intersection failure rates should be reviewed and the value of F set at the highest 20% of intersection failure rates.
- Spares for the current equipment in the field should always be available.
- A minimum of 95% of the detectors in the system should provide the system functions to the accuracy required for the application at any time.
- Qualifications for technicians for maintenance performed by the agency or by their contractor are described in Table 1.2. Although the specific technician position titles differ among agencies the table provides a spectrum of requirements for commonly used technician grades.
- Periodic checks of database parameters and controller settings should be performed. Procedures for software program and database configuration control should be adopted and utilized. Backups for software and databases should be maintained.
Table 1.2 Recommended Qualifications for Maintenance Personnel
|Replacement and repair of controllers, signals, wiring and other field
equipment. Works under direction.
|Skills include programming of traffic controllers, troubleshooting controllers
and ancillary equipment. Requires minimal direction. Provides direction
and training to Technician 1 level.
|Full supervisory responsibility. Supervises Technician 1 and Technician
2 levels. Greater technical knowledge than Technician 2 is required. Administrative
duties include ordering spares and supplies, contract administration, budgets,
provision for training.
|Education and Experience
- High school (minimum).
- Knowledge of electrical standards, codes, practices and repair techniques.
- Certification to IMSA Traffic Signal Level I within one year of employment.
Minimum of 2 years as Technician 1 plus:
- Certification to IMSA Traffic Signal Level II.
- Minimum of two years experience as Technician 1.
- Combination of training, education and experience for a total minimum
of five years.
- Certification to IMSA Traffic Signal Level II.
- Additional training beyond IMSA Traffic Signal Level II.
- Must be able to work for long periods in inclement weather.
- May be required to lift heavy objects, work from bucket trucks
|Same as Technician I.
Training practices should include the following:
- A plan to insure that the required number of qualified personnel will be available when required. The plan should prepare for retirements and other personnel losses.
- Support for training programs to achieve personnel proficiency requirements including the education required for continued PE and PTOE certification.
- Support for specialized training provided by suppliers and others relating to specific equipment or software currently in use or planned.
Formation and participation in a statewide or regional traffic signal management program should be considered. Regional traffic signal management programs allow agencies to formulate operations objectives that serve both the regional and local needs, facilitate consistent traffic signal operations throughout the region and provide a collective voice to improve the resources available for traffic signal operations and maintenance.
1.3 Conclusions and Recommendations
As stated by the National ITS Architecture Traffic Signal Operations is a strategy to manage the travel demand and flow of traffic on an arterial or roadway, At the beginning of the project, the guidance to be provided was envisioned to be defined, in large measure, by the resources used to accomplish these functions. The results of the literature review and the survey did not show a sufficiently strong correlation between resources provided and performance to justify defining the guidance strictly in terms of resources.2 During the course of the effort, it was determined that agencies have different approaches to the use of resources for the signal timing process and the primary guidance should be in terms of performance based criteria. This was termed Objective Oriented Operation (OOO).
OOO satisfies the objectives of the jurisdiction with regard to providing a quality of service that manages delay equitably and responds in a timely way to operations and maintenance requirements. It provides services consistent with the objectives of the agency, regional and national standards of performance. Given that there is no nationally accepted standard of performance, the performance requirements should be generally consistent with those identified by the NTOC Traffic Signal Report Card, as it our best current synthesis of what constitutes good practice.
The following conclusions and recommendations are largely based on the key items described for OOO in Section 1.2 and the staffing recommendations that are summarized later in this section and described in more detail in Section 2. It is recognized that agencies whose current capabilities differ significantly from these recommendations may require considerable time to reach this capability. It is, however, important that significant progress in this direction be made each year. If it is unlikely that agencies will achieve this capability in the future because their size is not compatible with the specialized requirements of OOO, it is recommended that other means, such as contract services or combining functions with another agency or jurisdiction be considered.
1.3.1 Management Approach
Agencies generally do not implement a systematic top-down approach to management. This type of approach requires a systematic, periodic, documented review, at least annually of the department's operations and the performance of the traffic signal system. Management deficiencies common to many agencies as determined by the study that should be resolved include the following:
- Availability of a mission statement including objectives.
- Availability of an annually reviewed and documented strategic management plan that describes the available system assets and operations, plans for improvement (including plans to update signal timing). The strategic management plan should also include plans for the correction of the types of deficiencies described in this section.
- Availability of a set of measures and periodic collection and evaluation of performance data relative to these measures. Mining and analysis of automatically collected data should be used to support this evaluation.
- Communication paths that are easy for the public to use.
- Resolution of issues and servicing of requirements involving other stakeholders. Typical requirements include signal preemption, transit priority, corridor coordination, coordination of signal timing with other agencies.
Many agencies do not retime signal with sufficient frequency nor do they have a systematic approach to determine the number of timing plans and their operating periods. Recommendations to correct these deficiencies include the following:
- Signal timing performance should be reviewed at periods established by management plans but should not exceed 30 to 36 month periods. Signals should be retimed using an accepted methodology. A methodology for determining the number of daily timing plans required as well as weekend and special function timing plans should be utilized.
- Review of system performance data to determine necessary phasing changes or intersection improvements.
- Systematic review of the number of timing plans needed and the periods for which they should be employed.
- Changes in functional requirements such as the need for pedestrian treatment, preemption, transit priority, diversion timing plans and evacuation timing plans should be identified and a plan developed for their implementation.
Once a notification of a critical field equipment failure is received, response times to repair are generally satisfactory i.e. within one hour during business hours and within two hours during non-business hours. Service deficiencies often occur under the following circumstances
- Most isolated traffic signals are neither connected to a traffic control system nor is provision made for monitoring their failure status. As a result, notification of equipment failure is often considerably delayed. It is recommended that greater emphasis be placed on providing such feedback to the cognizant maintenance facility.
- Most traffic control systems provide notification of critical equipment failure. It is recommended that when the traffic operations center is not staffed, this information be provided directly to the maintenance facility if the agency has not already made provision.
- Traffic detector repairs are often not made with the same response time as for critical equipment failures. It is recommended that a minimum of 95% of the detectors in the system should provide the system functions to the accuracy required for the application at any time.
1.3.3 Staff Qualifications, Training and Experience
Providing sustained excellence in traffic signal operations requires qualified and well-trained professionals throughout the operating agency. Traffic signal operations rely on expertise and support at all levels, from maintenance and engineering technicians to traffic engineers for signal operations and management. Specific job classifications vary between jurisdictions due to the size of the agency, number of signals operated and staffing levels. Regardless of the number of staff or the job classification, certain core functions must be performed to develop and sustain good traffic signal operations. These functions require specific knowledge, skills and abilities. The depth of knowledge needed varies by staff position and subject matter.
In order to stratify knowledge, skills and abilities and to provide an organizing structure for the analysis of training gaps, four generic categories of traffic signal professionals were defined. The following are descriptions of these categories or positions pertaining to traffic signal operations. It is important to note that the number of positions, titles and allocation of responsibilities can and should vary based on agency size and needs. For very small agencies, the traffic engineer for signal systems and the traffic signal design engineer may be a single individual. In some cases, these roles or some portions thereof may be performed by a traffic engineering technician. Therefore, the following descriptions are illustrative, and vary among agencies (11).
Traffic Engineer for Signal Systems:
This is typically a supervisory and advanced professional position responsible for directing the work activities pertaining to traffic engineering and operations, including the installation, monitoring, modification, maintenance and administration of all traffic signals and signal systems within the geographic boundaries of the jurisdiction. This position ensures that signal-related maintenance activities are adequately planned and executed and that there is an adequate inventory for signal related projects. The traffic engineer for signal systems is responsible for investigating and preparing specific recommendations for all traffic-related inquiries from both the public and governmental agencies and for providing overall traffic engineering expertise. This position plans, administers and supervises the installation, alteration, maintenance and repair of all types of traffic control devices. This position also develops and administers contracts for the installation or modification of traffic signal installations.
Signal Operations Engineer:
This is typically an advanced professional position responsible for, among other duties, managing, directing and supervising the planning, design, implementation, optimization and distribution of timing plans for traffic signal and signal system timing projects. This position reviews and approves plans for accuracy and clarity, conformance to standards, good engineering practices and reviews the provisions for the safety of the motoring public. Depending on the size of the agency, this position may be a supervisory position responsible for managing, directing and supervising assigned personnel on timing strategies, standards and practices for traffic signal and signal systems. The signal operations engineer may manage and supervise the development, approval, implementation and optimization of timing strategies at signalized intersections and signal system corridors. This position will coordinate, plan and evaluate computerized timing software packages. It also develops and recommends new strategies and tactics for traffic signal and signal system timing, including the development of performance criteria, methods of testing and an evaluation of performance.
Traffic Engineering Technician:
This position is typically responsible for advanced technical engineering support in the design of traffic signal control, communication systems and the operation of traffic signal systems. Depending on the size of the agency, there may be several traffic engineering technician positions with varying levels of expertise that correspond to designated technician levels. The position performs a variety of functions, including but not limited to the following:
- Provides technical assistance for traffic signal design, including phasing and calculation of timing plans;
- Uses computer-based software programs to develop optimized timing plans for individual intersections, corridors and/or networks;
- Maintains signal timing database;
- Maintains count database;
- Takes and responds to calls from the public pertaining to traffic signal operation;
- Conducts traffic signal studies;
- Conducts field reviews of signalized operations to identify problems and/or adjust timing plans; and
- Evaluates signal system operations in the field.
Signal Maintenance Technician:
This position is typically responsible for the installation, diagnostics and maintenance of all electronic equipment pertaining to traffic signal operation. Depending on the size of the agency, there may be several traffic signal maintenance technician positions with varying levels of expertise that correspond to designated technician levels. This position must have knowledge related to the application of sophisticated electronics and data communications technologies to traffic control applications, and be knowledgeable of new technologies applied to both new and old traffic control applications, including the variety of brands, models, types of equipment, systems and software that are available. Changes in traffic control technology and the greater use of telecommunications require increasingly more knowledge of electronics and greater computer literacy. The individual also requires sophisticated skills to troubleshoot and repair the latest generation of traffic electronic equipment.
Achieving OOO functionality requires a staff capable of providing the level of services required or capable of supervising qualified contract personnel. In many cases, besides the courses provided by equipment and software suppliers, there is little support for or encouragement of training. Professional training to achieve the recommended competence levels should be encouraged and supported. Required proficiency levels are summarized below.
- Agency management and supervision of signal timing and operations should be supervised by a personnel with a Professional Engineer and a Professional Traffic Operations Engineer qualifications.
- Maintenance technicians should conform to the requirements shown in Table 1.2
Achievement of OOO capability requires adequate staffing by qualified personnel. Staffing requirements are driven by the objectives (Table 1.1), performance measures selected and agency specific considerations described in Section 1.1. The following staffing guidelines are based on operating agencies interviewed under this project and other projects.
- A staffing level of 75-100 signals per engineer for agencies that operate a minimum of 150 signals will be appropriate to support the Constrained Ideal Traffic System. Smaller agencies will likely require fewer signals per engineer because economies of scale may be difficult to realize.
- A staffing level of 30-40 signals per technician for agencies that operate a minimum of 150 signals will be appropriate to support the Constrained Ideal Traffic System. Smaller agencies will likely require fewer signals per technician because economies of scale may be difficult to realize.
Giblin and Kraft (12) estimate that a per intersection annual average of 42 hours is required for preventive maintenance, 15 hours for response maintenance and 3 hours for design maintenance for a totals of 60 hours. With an estimate of 1627 hours per year of productive time available per technician, they estimate that one technician can service 27 intersections. More technician labor is required if the agency has a greater percentage of complex intersections.
1 These criteria may be modified where agencies utilize adaptive systems or ACS Lite type systems.
2 The respondents estimates of detailed resource information may be in considerable error and the subjective character of agency performance estimates contribute significantly to this lack of strong correlation.