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OCR for page 198
A.~.4 Computer Considerations in Communication
by MatlLx Corporation Raleigh, North Carolina
Background
New transportation management strategies require the capabilities of modern computer
systems. In the past, highway corridor control systems used mainly Model 170 or NEMA
controllers; however, new intelligent highway applications require more traffic monitoring
and processing than before. This need has created demand for what is commonly referred to
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Figure A.1.41 Example VICE bus-based 2070 controller for ITS
as an Advanced Transportation Controller (ATC). As a result, ATCs are now being deployed
in highway applications In ever-increasing numbers.
What Is an ATC?
The definition vanes, since its functional characteristics often differ from one application to
the next; however, there are severe common factors to the new generation of ATCs:
· A VME computer bus (a nonproprietary computer bus structure)
~ Operating temperatures of -34° to +74°C
· Off-the-shelf real-time operating system (e.g., OS-9.
L..\NCHR~Phasc2.1pt\2070.qx ~NCHRP 3-51 · Phase 2 Final Report
A1-190
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The 2070
An Open Architecture VMEbus-based Advanced Transportation Controller
Overview/App/ications
The 2070 is an ATC conceived by California Department of Transportation (Caltrans), the
City of Los Angeles, and others to provide distributed computing, control, and
communications within traffic infrastructures. It conforms to the comprehensive
Transportation Electncal Equipment Specifications (TEES) developed by Caltrans.
The 2070 not only augments the role of traffic operations centers, but it also provides
features and functionality not provided by previous generations of traffic controllers. The
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Figure A.1.42 MC68360 OPUS He 2070s VMEbus Card Cage
2070 is built upon a nonpropnetary,
configurable, open architecture computer
platform that accommodates a wide range
of functional modules. These modules
(plug-in computer boards) conform to the
well-established standard VMEbus
specification. The VMEbus specification
defines mechanical and electrical
characteristics to establish compatibility
from one manufacturer to another. The
selected combination of modules and
applications software determines the
functionality of an 2070. Two basic
configurations are available to ensure 2070 compatibility with existing NEMA and Mode}
170 controller cabinet standards: Me TS3 and the 2070 respectively.
The 2070 supports sophisticated applications such as adaptive intersection control,
integrated corridor management, emergency surveiliance/pre-emptive management,
emergency call box communications, etc.
i
Its expandability allows it to control many more devices than older controllers. A single
2070 can control several ramp meters, speed monitors, and changeable message signs
(CMS), in addition to environmental sensors and cameras. ~ previous highway designs,
each function required a controller. Also, video processing modules can be instaNed In the
2070's VMEbus. These modules detect and determine speed, ciassiDcation, and travel time
from one controller point to another. See page 4 for an example system configuration where
the 2070 is cast in the role of Intelligent Multiplexer.
r - ~ ~
L:WCHAP\Phase2.rpt\2a70.qx ~NCHRP 3-51 · Phase 2 Final Report A1-191
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With the 2070, contractors have fewer cabinets and communication lines to install which
streamlines project requirements. Aside from lower installation costs and shorter
deployment schedules, an 2070 installation is also simpler for the DOTs to maintain.
Major Subsystems of the 2070
VMEbus/Computer Platform (see Figures A.~.4-] ar'`A.~.4-2)
This platform provides the brains that coordinate other 2070 subsystems and manages the
key 2070 functions-control and communications. It incorporates a computer processor
module resident in art expansion chassis that provides four expansion slots for other
functional modules. The combination of modules in an 2070 is user selectable to manage the
applications at hand.
The computer module incorporates a high-speed 32-bit computer chip. It integrates
advanced communications capabilities such as SDLC, HDLC, Ethernet, etc., and can
connect to T! telecommunications lines. Its features support high bandwidth
communications .
Front Panel
The 2070 front pane! assembly consists of two keypads and a 4x40 LED display managed
by a dedicated microprocessor for high display update rates. The interconnection to the main
V~bus processor is a serial differential interface which provides electrical protection.
Fred Inpu!JOu~ut Module
Field I/O Modules for the 2070-170 and 2070-TS3 are different in format but provide the
same functionality: the interface to to load switches and detectors. Like the Front Pane]
Assembly, the Field I/O Module incorporates a dedicated microprocessor. It provides pre
scanned or pre-collected input data at rates of 1,000 samples per second without interrupting
the primary VME control processor.
~2
2070-7
EIA-232
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t2 lo.
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170 C1 & C11 Connectors
OR
Name MS A, B. C, & ~ Connectors
L:\NCHRP\Phasc2.rpt\2070.qxd
4x40 1
LCD Dam I
~ ~ LIP
11 1 11 Eu Poll
2070~ 1~0
Front Panel
NCHRP 3-51 · Phase 2 Fmal Report
DC Loo
Po_
t t
2070-
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Supply
t
AIC
FgureA.1.43
2070 Architecture
A1-192
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2070 Modem Module
This module provides the communications link between the traffic operations center and
remote 2070s which might be acting as regional communications hubs to concentrate, pre-
process, and communicate data from multiple intersections, etc. System modularity allows
for older Bell 202 modems, as well as higher-speed modems and fiber interfaces (including
DO-. One modem module may be interchanged for another at any time.
2070 Communications Module
Two general purpose senal channels are provided. They can be configured as ElA-
232/422/~85 and over electrical interfaces.
Software
The 2070 real-time environment is based on OS-9, an industry standard operating system.
The 2070 incorporates diagnostic and various self-test software. Application software is not
integral to the 2070. Rather, application software is available from specialized software
suppliers, integrators, consultants, and DOTs.
Maintenar~ce/Rel~abitity
Since the 2070 is modular, it enjoys the efficiency of a board-swap maintenance regimen.
The 2070 is designed to operate in harsh environments from -34° to to +74°C. Software
changes/upgrades are performed by serial downloads, elilIiinatirlg Me need to handle the
elc~onics. Thus, one of the primary causes of failure "handling" is eliminated.
Table A.~.4-1
Requirements versus Capabilities of Various Controllers
Features NEMA MODEL NEMA 2070
TS-1 170 TS-2
Industry stanclard, open architecture computer No Yes No Yes
Based on openly available real-time OS No No No Yes
Use of high-level languages No No No Yes
Powerful microprocessor . No No Yes Yes
Ability to support T1 communications rates No No No Yes
Expandabiltyof number of 1/0 points No No Yes Yes
Ability to support NTCIP No No Yes Yes
Modular architecture for maximum flexibility No No No Yes
Scalable for future growth & technical advances No No No Yes
L.\NCHRP\Phase2erpt\2070.9xd NCH~P 3-51 ~Phase 2 Fmal Report A1-193
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Example Application
The 2070 as an Intelligent Multiplexer
TOG
Computers
Ethemet
Figure A.1.W 2070 in He Role of Intelligent Multiplexer
ElA-232 Multidrop
~ Modems to
Intersection
_ _ . ..
2070
^ ~ is IMUX ~ Controllers&
Other Devices
USA
Router
.
.
EIA-232 Multidrop
DS-1 2070.4 . ~ Modems to
IMUX ~Intersection
Other Devices
~1 1
EIA-232 Multidrop
2070 ~ ~ Modems to
IMUX ~
Intersection
Controllers &
Other Devices
ATCs are often thought of as field processors that can only "control" traffic devices. How-
ever, ATCs are much more capable and can be applied in applications calling for fi~nction-
ality beyond the capabilities of NEMA or Mode! 170 controllers. This example demon-
strates a system configuration where the 2070 plays a key role in providing powerful
communication capabilities econom~caDy.
Communications is a critical element for most ITS applications. In many modern ITS
designs, communications paths run from computers in a traffic operations center (TOC) to a
router. The router's main purpose is to route and exchange data between the office network
(e.g., Ethernet) and an external telecom interface (e.g., DS-1). From there, data is transferred
to 2070s that perform an Intelligent Multiplexer function and are positioned regionally. The
2070 Intelligent Multiplexers route data to the actual devices (e.g., intersection controller,
CMS signs, etc.), often over multidrop modem interfaces.
This example is significantly different from simpler point-to-point communications
methods. This design minimizes wiring from the field and the ability to use open
architecture standards such as ATCs, telecommunication interfaces and equipment, office
networks, etc. Additional benefits include lower maintenance costs, simpler installation, and
better reliability. This architecture is also adaptable to future requirements. For example, it
can be used for new adaptive intersection condom algorithms Hat use distributed
architectures and require significantly enhanced communications capability.
L.\NCHRP\Phase~rp~O.qx ~NCHRP3-51 · Phase2FinalReport A1-194
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User Acceptance and Demand
Several Integrators have deployed open architecture computers In traffic management
applications over the past eight years. Many of these systems were configured from
VMEbus modules running off-the-shelf real-time operating systems, like OS-9. Most of
these initial deployments were for highway control and toll applications,where capabilities
beyond those offered by the Mode] 170 were required. Over the last two years, a ground
swell has taken place toward ATCs. Caltrans has spent considerable resources developing
the 2070 specification, and the 2070 is intended to be the next-generation controller for
Caltrans' rRs applications. Interest in ATCs has grown so strong that U.S. DOT's
Transportation Research Board (TRB) has set up a task force to track MC developments
and disseminate information. ATCs are now being deployed In highway management, toll
collection, intersection control, and other transportation applications.
~:WCHR~Phase2rprs2070.qxa NCHRP 3-51 · Phase 2 Final Report Al-l9S
Representative terms from entire chapter:
traffic operations
