Click for next page ( 48


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 47
47 CHAPTER EIGHT CONCLUSIONS The study findings were based on a literature review and two signal timing plans, survey respondents indicated that ATCSs electronic surveys: a shorter e-mail survey for vendors or devel- are only tools for traffic management and they need to be opers of 10 major adaptive traffic control systems (ATCSs) supervised and controlled by skilled engineering staff. Proper and a main website-based questionnaire for agencies that training and acquisition and retention of expertise within an deploy ATCSs. The main survey was originally distributed to agency were reported as the most important factors for allevi- 42 agencies that run ATCSs in North America (United States ating institutional barriers for ATCS deployment. ATCS opera- and Canada) and several dozen locations around the world. tions are often not perceived as being difficult; however, it Numerous follow-up requests were made, by e-mail and appears that ATCS users are not often given the opportunity to phone, to remind agencies that had not yet responded, asking learn how to fully operate their systems. One of the reported them to participate in the survey. Responses were obtained operational problems indicated a lack of the basic knowledge from 34 of 42 agencies in North America, an 81% response for operating an ATCS. A majority of the ATCS users rely on rate. Also, 11 responses were received from agencies in other in-house expertise, which is more an indication of not having countries. Of the North American agencies, 42% were munici- adequate resources to hire outside support than that ATCS pal entities, 20% were counties, 13% were state agencies, and users are fully trained to control and operate their systems. In 25% were other. general, ATCS users would like to acquire additional expertise; however, the agencies do not have enough financial resources The survey indicated that ATCS agencies deploy their to acquire comprehensive training, and most of the agencies ATCSs in operational environments where the systems are are short staffed. ATCSs are considered more operationally known to provide the best performance. Most of those inter- demanding than conventional traffic signal systems; however, viewed have 10% to 30% of their traffic signals under the agencies are not able to support these systems in the same way ATCS. Handling daily and weekly fluctuations in traffic flows they support conventional traffic signal systems. Unlike con- is the highest ranked reason for ATCS deployments. When ventional systems that are maintenance-intensive, ATCSs procuring an ATCS, agencies frequently consider multiple sys- require more emphasis on the expertise necessary to operate tems. On average, an ATCS installation takes approximately their sophisticated operations. This switch in the type of labor 18 months, from the time when funding is made available to the (from maintenance to operations), which is needed to support time an ATCS becomes fully operational. Most of the ATCSs proper ATCS operations, is often not recognized by an agency that have been deployed during the last 20 years are still in until the ATCS is already deployed. This inability to recognize operation. If an ATCS is shut down it is usually the result of the need for additional operational expertise in a timely man- several negative factors. Agencies frequently expand their ner can adversely affect the ATCS performance. If the agency ATCSs and, in general, most are satisfied with their operations. is disappointed with the performance, it will be reluctant to expand on the existing system or to procure new ATCSs. Review of the most widely used ATCSs showed that var- ious systems use similar strategies to cope with fluctuations Detection requirements for an ATCS are slightly higher in traffic demand and distribution. However, each tool is than those for conventional traffic-actuated control systems. unique and without direct comparison it is difficult to com- Most of the ATCS users are satisfied with the way their system pare the algorithms and adaptive logic of the various tools. handles minor detector malfunctions. Some ATCS users have Field implementations of various tools are even more unique difficulties with the handling of ATCS-specific hardware, than their logics, which makes direct field evaluations expen- although this is primarily an issue that could be resolved with sive and therefore impractical. For this reason, among others, better training of the technical staff. ATCSs mainly operate on very few studies in the literature provide evidence that the Windows-based platforms and are sometimes integrated with operational concepts of one particular ATCS are better than one of the available Advanced Traffic Management Systems those of another. (ATMSs). Integration with an ATMS, which is not common, has become more frequent with recent ATCS implementa- There is a considerable need for expertise to ensure a tions. As perceived by most of the users, ATCS software is successful ATCS implementation. Although many agencies one of the components that need improvement. Interestingly, implement ATCSs to reduce labor-intensive maintenance of ATCS users do not find that ATCS communications cause

OCR for page 47
48 many more problems than the communications of conven- Overall, most of the surveyed ATCS users (73%) would tional traffic control systems. However, communications play install the same system again. Users with more signals under a much more important role in ATCS deployments and for this an ATCS have more satisfactory experiences with ATCS reason need to be regularly maintained, which represents one operations. More signals under an ATCS attract more attention of the major operational costs for ATCS users. within the agency, and therefore more resources to operate and maintain the ATCS, more staff to develop and maintain The survey results showed that ATCS installation costs in-house expertise, and finally more attention from ATCS per intersection are approximately $65,000 and are higher vendors. Smaller systems are inclined to have more problems than previously reported. Interestingly, results showed that securing funding and hence their overall experience with ATCSs require less funding for physical maintenance than ATCSs is not as positive. conventional traffic signals. This finding contradicts com- mon belief present in the traffic signal community that main- Although specific recommendations were not requested in tenance of ATCS detectors and communications is costly. the survey, survey recipients suggested the following research to improve knowledge of ATCS implementations in the United When ATCSs are evaluated most agencies prefer to hire States and other countries. outside consultants, which primarily perform field evalua- tions through a set of before-and-after studies. A majority of Explore establishing a coalition for Adaptive Traffic the user evaluations reported that ATCSs outperformed con- Control, which could serve as a framework for exchang- ventional traffic signal systems. ing experiences and lessons learned about ATCS deploy- ments. Agencies with smaller budgets for ATCSs may The benefits of ATCS deployments are not easily observ- particularly benefit from such a coalition. One of the first able in oversaturated traffic conditions. Although ATCS priorities could be to investigate factors that represent users find that their systems may delay the start of oversatu- barriers for new agencies to deploy an ATCS. ration and reduce its duration, they are not recognized as a Research into funding operations by an ATCS includ- cure-all for such traffic conditions. However, modifications ing the Transportation Pooled Fund Program and other of an ATCS to reduce oversaturation is often beyond the similar programs that could provide resources to con- competence level of ATCS users; therefore, there is little duct further studies on these systems to address the data available to draw conclusions about ATCSs' perfor- most important and urgent issues. mances in oversaturation. More study is needed to estimate the true benefitcost ratios of ATCS deployments. There is a need for com- Most users do not perceive that the performance of their ATCS degrades over time. Public education campaigns about prehensive evaluation studies that would show all of the ATCS deployments are not very common and effective, as costs and benefits of an ATCS deployment (including indicated by most ATCS users. Also, not many ATCS agen- investigation of the long-term operational savings result- cies conduct public perception surveys. Those agencies that ing from long-term changes in traffic demand). do reported that results from such surveys are supportive ATCS agencies could be encouraged to document and approximately 50% of the time. analyze implementation issues (i.e., staff retention) to identify the costs and benefits associated with the use of ATCS agencies were mostly generally satisfied by their sys- an ATCS when compared with the deployment of con- tems' ability to provide what was observed as "efficient opera- ventional traffic control systems. Potentially, these doc- tions" and to adjust to within-day and day-to-day traffic fluctu- umenting efforts could be a requirement imposed, and ations. Negatives were mostly related to difficulties in learning financially supported, by federal authorities. Demon- how to operate the system and the hardware (primarily com- strating benefits can promote more extensive and more munications). Lessons learned can be summarized in four cat- appropriate use of ATCSs. egories, which represent pre-deployment actions necessary for More research is needed to investigate various funding successful ATCS implementation: better local support from sources used to deploy ATCSs. Research on how much vendors; better planning for in-house operational and institu- funding is necessary to support various components of tional support; good preparation of the infrastructure (detection ATCS installations [e.g., cost of hardware (electron- and communications); and detailed pre-installation evaluation ics), software, and labor (installation, maintenance, and to estimate operational benefits. Major reasons that prevent operations)] is also needed. It could be also investigated ATCSs from further expansion include the high costs related to how agencies make decisions to deploy ATCSs and operating and maintaining the system (e.g., employing and whether decisions are made in coordination with oper- training the staff). ational staff.