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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
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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
