Click for next page ( 31

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 30
30 Major detection failures degrade ATCS operational per- Approximately 80% of interviewed agencies reported that formance. Under such conditions, an ATCS may continue they are familiar with the hardware that their ATCSs use. The to work as if nothing happened, and in the best case sce- 20% who reported that they were not completely familiar with nario it will work based on the historic data or as an actuated- the hardware emphasized the following problems: coordinated traffic signal system. If the background actuated- traffic operations are designed properly the system may Special protocol modifications were made to support continue to work for hours or days before any operational existing hardware [i.e., Virtual Machine Environment change is noticed. For this reason it is important that ATCSs (VME) processor cards, second central processing unit have the ability to alert operators about major detection fail- in 2070 controller], ures. Although most ATCSs have such ability, 16% of ATCS New hardware components (digis, modems, interfaces) users reported that their system continues to operate as if were not used before by the agency ("black box" syn- nothing happened, without notifying the operators about drome), and detector malfunction. Approximately 53% of the ATCS users Training was necessary for field technicians to learn reported that detector malfunction triggers an alarm and noti- how to use new controllers and other hardware. fies the operators. When it comes to "safe mode" operations during the major detection failure, 26% of ATCS users indi- SOFTWARE cated that their systems switch to off-line TOD operations, whereas approximately 25% answered that their ATCS start Another key component in operations of an ATCS is the using historic traffic profiles. friendliness (interoperability and usability) of the ATCS soft- ware. In a category of questions that addresses this topic, ATCS users were asked to provide information about the HARDWARE operating systems and platforms of their systems, as well as the integration of their systems with Advanced Traffic Man- ATCSs are usually installed when agencies are ready to radi- agement Systems (ATMS). cally change traffic signal operations on arterial networks. Usually such changes include the replacement of existing Windows-based operating systems are used at approxi- local intersection hardware (i.e., controllers or controllers and mately 57% of the interviewed agencies. Ten percent of ATCS cabinets) that may be reaching the upper end of its anticipated users run their systems on Unix-based operating systems. life span. However, installation of the hardware necessary to Open VMS, an operating system mostly used as a SCOOT operate an ATCS usually involves installation of components platform, was reported by 14% of the interviewed agen- not familiar to the local agency's staff. Therefore, the prob- cies. It is interesting to note that only 14% of ATCS users lems that may arise with new hardware have two compo- reported using an Open VMS operating system. Considering nents: (1) technical (quality of the hardware components) and that almost 35% of the interviewed agencies use SCOOT sys- (2) institutional (training necessary to master operations of tems, which almost unanimously still run on Open VMS (there new hardware). are only few installations in the world where SCOOT runs on a Windows-based platform), the results indicate that some of If the central hardware and local controllers do not meet the ATCS users are not sufficiently familiar with their ATCS. ATCS requirements, system performance will suffer. In the past, some of the ATCS deployments in the United States were When asked how user-friendly they consider their ATCS shut down because of the problems with local traffic controller software, only 18% of the interviewed agencies responded or central system hardware. Incompatibility of imported local that their system's software is very friendly. Results from this controllers (previously required for operations of some inter- part of the survey are presented in Figure 8 and they show that national ATCSs), problems with communication between the ATCS software generally keeps up with users' expectations. controller's unit and coprocessor card, and uncommon central However, almost one-half of the ATCS users are not very hardware are only some of the examples of such hardware satisfied with the way their ATCS software works. Software problems. Table 9 shows which traffic controller types are development is a time-consuming and costly process. Unlike most commonly used by U.S. agencies. International agen- common Windows-based applications (e.g., MS Office) cies that deploy ATCSs mostly use controllers that run their ATCS software is developed for (and sold to) a couple of local controller standards (i.e., Novax controllers in Canada, hundred users (at most) around the world. Also, each ATCS SCATS controllers in Australia, etc.). deployment is somewhat unique (various hardware and soft- TABLE 9 TYPES OF TRAFFIC CONTROLLERS USED BY ATCS Traffic Controller Type Percent of Agencies NEMA TS-1 30 NEMA TS-2 35 2070 ATC 34 Model 170 1

OCR for page 30
31 Unfriendly; 6; 14% Very friendly; 8; 18% Neutral; 15; 34% Friendly; 15; 34% FIGURE 8 Friendliness of ATCS' software. ware elements need to be integrated), which sometimes Results from the survey showed that 21% of ATCS users requires software customization that is beyond the financial do not have an ATMS. Seventeen percent of those users who support allocated for ATCS deployment. Under such cir- do have an ATMS do not have their ATCS and ATMS inter- cumstances it is understandable that ATCS software does not faced. Those ATMSs that are the most frequently used are always keep pace with modern software developments and ACTRA, MIST, and i2TMS with 10%, 10%, and 7% of ATCS therefore may appear somewhat archaic to ATCS users. With users, respectively. Approximately 48% of interviewed ATCS an increase in the size of the base of ATCS users it is expected users utilize other ATMS (T2000C, Aries, Sitraffic, Alcatel that the gap between ATCS software and general software ATM, TMIS, etc.). trends will decrease. One of the major ATCS software functions is to report Although ATCSs can independently control traffic signals malfunctions and other diagnostics of its hardware and soft- they are often integrated with an ATMS, which is used to ware components. ATCS Graphical User Interfaces usually manage the traffic signal system, providing such functions as provide a full range of operator commands and monitoring Graphical User Interface, archived database management, functions. Some of the typically displayed data for monitor- and a graphic display system showing signal status, operating ing operations at an intersection are: effectiveness, and communications. The ATMS provides inte- grated control of a variety of surface street traffic management Lamps on/off/flashing functions, including traffic signals, dynamic message signs, Current phase demands closed-circuit television (CCTV) cameras, and vehicle detec- Detectors occupied tion. If an agency runs an ATMS and wants to deploy ATCS Current cycle time (or vice versa) it is often important that these two tools are inte- Operating mode grated or interoperable in order to deliver improvements asso- Alarms ciated with both systems. However, such integration can be Current phase very difficult to execute, owing to a number of reasons such as Elapsed phase time. costs, intellectual rights, etc., and is rarely performed. How- ever, some of the ATMSs are preprogrammed to offer integra- Most of the interviewed ATCS users (95%) reported tion with certain ATCSs, in which case an ATCS runs as a sin- that their ATCSs are capable of reporting necessary diag- gle option among various traffic control platforms within the nostics. Figure 9 shows how system alarms are logged, ATMS [e.g., ACTRA--SCOOT, Management Information viewed, and managed in SCATS' Alarm Manager. Equally System for Transportation (MIST)--OPAC]. important parameters that need monitoring are operational