Is it possible for a traffic control center to reach maximum potential when it comes to managing traffic on a local basis?
A traffic control center can maximize its functions in
regards to its ability to monitor, manage and react to certain traffic conditions.
By increasing the efficiency and reliability of a traffic
control center beyond the limitations presented by a localization of the
traffic information process, the TCC may benefit in that it may also provide
for 24/7 operation in locations where it otherwise may not be possible.
Furthermore, it may also provide redundancy so that operations need not cease
when a local TCC is unable to operate—during a power loss for example.
Concurrently, the TCC’s management can provide an exchange of information
when a major incident affects traffic flow and travel decisions across local
TCC boundaries.
This was the case with the Coordinated Highways Action
Response Team (CHART) program in the state of Maryland. Originally introduced
as the Reach the Beach Program in the 1980s, CHART evolved into a
multi-jurisdictional, multi-disciplinary program far beyond the original focus
of improving travel to and from the eastern shores of Maryland. This evolution
eventually included and focused primarily on the state’s need for a
distributed freeway traffic management system primarily for the metropolitan
Baltimore, Washington, D.C., Frederick and Annapolis areas, as well as the
entire state.
CHART is managed by a board of directors that consists of
senior technical and operating personnel from the Maryland State Highway
Administration, the Maryland Transportation Authority, the Maryland DOT, the
Maryland State Police, the Federal Highway Administration, the University of
Maryland Center for Advanced Transportation Technology, as well as various
local government representatives.
“The CHART board was designed from the beginning to
make sure that the agency and jurisdictional managers responsible for traffic
management in Maryland were represented at a high level to ensure the proper
deployment of incidence response and intelligent transportation systems in
Maryland,” said Richard R. Dye, CHART systems administrator for the
Maryland State Highway Administration, Hanover, Md.
At the conclusion of the 1990s, advances in traffic
management technology, in concert with the increased demands on the success of
the initial statewide implementation of the CHART system, convinced the
Maryland State Highway Administration that an upgrade was necessary to improve
CHART’s system utility and reliability.
The Maryland SHA wanted a more fully integrated roadway
monitoring and travel advisory system, and they envisioned the development of a
system-wide software architecture that would integrate its operation with other
transportation agencies in Maryland as well as neighboring states.
“However, the need for the original software was not
expandable for the additional agencies that needed to coordinate the traffic
management effort and the network design was becoming too costly to
maintain,” said Dye.
Eventually, the partnership of the Computer Sciences Corp.,
Hanover, Md., and PB Farradyne, Rockville, Md., designed and developed the
Maryland SHA’s new statewide transportation management system known as
CHART II.
Including the viewpoints of the many different agencies
involved in CHART, the development of the CHART II systems involved the
application of modern software development processes broken down into a series
of multiple builds so that each could be better detailed, designed, priced,
built and accepted.
“CHART II expanded the original software design to
further automate the traffic management capabilities of the CHART system as
well as distributed the incident management information and field equipment
control to a much more flexible, much more robust and yet more affordable
network,” said Dye.
Released in stages
CHART II is a comprehensive state-wide traffic management
system design which encompassed separate detailed design, build and acceptance
testing of four distinct released increments spread over an eight-year period.
The very first release of CHART II in 2001 implemented a
new, distributed architecture that allowed the viewing of statewide cameras at
multiple concurrent facilities as well as hierarchical control strategy that
allowed control of cameras at different facilities depending on user rights.
Other initial releases provided basic dynamic message sign
capabilities and the foundation for the rest of the CHART II, which included
user login functions and methods for communicating between the different parts
of the software. Subsequent releases included adding more dynamic message signs
and incident management capabilities; the capability to collect detector data
and have this information sent to the website (www. chart.state.md.us); and the
deployment of an advanced queuing mechanism that displays the proper message
when there are several events trying to use the same sign or highway advisory
radio.
“Next will come the map graphics user interface, more
automated re-sponse, then integrated video control, and more integration of
regional transportation operations centers (TOC),” said John Schumitz,
CHART project manager for PB Farradyne. “Releases are planned
approximately through the year 2006.”
“Other logic that has been built into these early
releases that will support decision management and artificial intelligence
tools of later builds include auto-formatting of DMS messages from straight
text input using MULTI-STAGES, text-to-speech for the HARs and auto-fill of
incident forms depending on the type and location of incidents declared,”
added Dye.
Front-line information
As mentioned above, system development proceeded in
incremental steps. System functionality for the four software releases were
identified, each comprising multiple builds. The development of large software
systems in increments allowed for greater flexibility in design, more effective
management of the development process and allowed the Maryland SHA to take
advantage of a new operating capability as the system grew.
The Maryland SHA intended to use the CHART II system to
manage traffic throughout the state and establish high-level requirements for
integration with external systems. Computer Sciences Corp. and PB Farradyne
accomplished this process by actively participating in envisioning the system
and its business area architecture developed under the Software Engineering
Institute’s Capability Maturity Model Level 3.
As part of the procurement process, Computer Sciences Corp.
and PB Farradyne system developers conducted an extensive process of developing
and modifying graphical user interface (GUI) prototypes while working in
partnership with the Maryland SHA personnel that would actually be operating
the system.
System requirements were determined through extensive
one-on-one discussions with system users and administrators, including the
development and modification of GUI prototypes. This process entailed frequent
reviews of issues and priorities as the design progressed.
“Although the primary motivating force for the
redesign of CHART was the decision to distribute the system in a more
cost-effective way among multiple agencies, there were some substantial
benefits to the operators,” said Dye. “The biggest changes that the
operations staff has already noticed about CHART II is that they were involved
in-depth in its design.”
This was evident when the system design process featured an
extensive set of meetings to establish prioritized access to field device
control under different operating scenarios.
New field equipment management stations also were addressed.
CHART II was designed as a completely distributed system that provides control
of field equipment from TOCs located throughout the state.
“By distributing the control of field
equipment—DMSs, remote traffic speed monitors—to multiple PCs in
the field, once again primarily for cost reasons, gave the benefit of fewer
losses of communications due to redundant paths to these new field management
stations,” said Dye.
In the field
While changes were aplenty behind the scenes, new field
devices also were being installed, in addition to the equipment already in
place.
CHART II is able to monitor traffic conditions and control
traffic management devices throughout the state. These applications include 60
CCTV cameras, 22 snap-shot cameras, 32 HARs, 30 portable and 60 permanent DMSs,
60 side-fired radar traffic sensors and 55 weather detectors.
As is common, problems arose when the field devices,
manufactured by a number of different vendors, were integrated.
“CHART II integrates about nine different types of DMS
from seven different vendors,” said Schumitz. “Working out the
similarities and differences to build a common piece of software to operate
them is always a challenge and you are guaranteed to run into things in the
field that don’t operate as described in the documentation. We have run
into a couple of network communications problems that caused some unexpected
software behavior, but these were corrected and where possible the soft- ware
was changed to be more robust or at least notify the operator when the network
fails.”
Architecture design
CHART II also features completely distributed system
architecture. CHART II software is resident on computers located in
transportation operation centers in several locations throughout the state.
Through the use of asynchronous transfer mode switching technology, video
information can be shared among the local TOCs and with the statewide CHART
operations center in Hanover, Md. Any of the local TOCs can assume the
responsibility of the state operations center or any other TOC, providing complete
system redundancy.
“Field devices generally remained the same although
there have been some communications systems changes,” said Schumitz.
“CHART II is being done as part of a major communications system change.
A new ATM network has been installed to support the distribution of traffic
video anywhere in the state and communications to other field devices also are
supported on the new ATM network and part on telephone company circuits.”
The distributed system architecture design of CHART II
provides for information from field devices to be sent to and stored at the
nearest local TOC, greatly reducing communications costs. An Oracle database
can automatically retrieve requested information from wherever it is stored in
the distributed system.
All functions are accessed through a single map-based GUI,
designed by the system users through the prototyping process. By pointing to a
location on the map, system operators can view all the relevant information on
that location in the database.
When an incident is confirmed, pre-stored response plans,
involving pre-developed DMS and HAR messages for devices in the vicinity of the
incident, are displayed and can be easily approved or modified by the system
operator.
“The users see a more stable and more integrated
system. It also is a system that uses input from them in its design so that it
better supports them in the way they work—we regularly consult with the
operators and managers regarding details of system design,” said Schumitz.
“The manual paper logs the operators had to keep to record communications
and incident information are now in an electronic form and automated to the
extent possible. This helps reduce errors, makes the information more readable
and accessible and supports them in im-proving their operations.
Maryland and beyond
Originally, CHART was implemented to improve the ability of
the Maryland SHA to monitor traffic conditions and issue travel advisories for
550 miles of highway and its arteries.
“CHART II demonstrates the success that can be gained
by agency and consultant working closely together to define and implement the
system,” said Schumitz.
CHART II also is a model architecture for a statewide system
and even a multi-state system, one that can be altered and added to with a
minimum of software development effort.
Other state TCCs are likely to continue to implement similar
systems. While most may not have the statewide distribution capabilities of
CHART II, many perform similar functions on a local scale. Maryland has agreed
to share the CHART II software with other states, several of which have
expressed an interest in implementing the CHART II system.
“Several agencies are already planning their own
modifications to the base CHART II software, which MDOT has decided to make
available free-of-charge to anyone who wants it,” said Dye. “New
releases of CHART II—starting with release 2, which is in detailed design
right now—will continue until the detailed design is complete. Then a
firm, fixed-price bid will be negotiated to build this well-defined piece of
software.” TME
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