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Traffic Information Systems
Application: Network-Enabled Traffic Information System
Quatech Products Used: QSE-400D
4-Port RS-232/422/485 Device Server
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Intelligent Transportation Systems serve many purposes from providing
motorists with traffic information via variable message signs, to monitoring
traffic flow using remote controlled cameras, to managing that traffic
flow using lane control signals. A wide variety of serial devices are
used in these systems in addition to those just mentioned, such as pavement
sensors that detect traffic volume at lights, loop detector networks used
to track traffic movement and radar and sonar vehicle detectors--to name
just a few. Traditionally these systems were implemented with PCs located
in roadside NEMA enclosure connected to the traffic control devices via
serial cables. As shown in the above diagram, a single device server can
be used to replace the PC--a significant cost savings. In addition, by
using the device server, system performance is significantly enhanced
because not only is real-time data available for analysis by the Traffic
Management Center, this data can also be disseminated to drivers via message
board alerts and via the Internet. In addition, lane control signals,
traffic lights, and ramp meters can be used to mitigate congestion.
Thus, network-enabling the serial traffic information system equipment
significantly increases its value as a traffic management and control
instrument. Further, it enables the system to comply with NTCIP requirements
that the devices be available to all authorized jurisdictions, in addition
to the Traffic Management Agency that owns the system. With device servers,
the remote serial equipment can be network-enabled using the fiber LAN
network already in place along most major roadways. The devices can then
be accessed by any authorized PC or server on the network, regardless
of operating system, just as if it were directly attached to a local COM
port. For example, as shown in the diagram above, two authorized jurisdictions
running Unix and Linux servers can access and control the devices even
though the core Traffic Management Server is a Windows-based system. And,
while only one computer at a time can access a particular port, multiple
computers running different operating systems can access different ports
on the device server simultaneously.
Other Intelligent Transportation Systems Applications:
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