Improving Traffic Signal Management and Operations: A Basic Service Model
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.
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:
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 do not 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 self-assessment, 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.
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.
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 self-reinforcing 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 do not 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.previous | next
United States Department of Transportation - Federal Highway Administration