User's Manual

Installation 7
3. Description
This section provides a general description of the
3M™ Opticom™ GPS Priority Control System and a
detailed description of the vehicle equipment
3.1 Opticom GPS System
The system assists authorized priority vehicles
through signalized intersections by providing
temporary right-of-way through the use of
common traffic controller functions.
The Opticom GPS system consists of the
following matched components:
•= Vehicle Equipment —
•= Radio/GPS module containing a GPS
receiver with antenna and a 2.4 GHz
transceiver with antenna
•= Processing module
•= Intersection Equipment —
•= Module containing a GPS receiver with
antenna and a 2.4 GHz transceiver with
antenna
•= Phase Selector
•= Auxiliary Interface Panel
•= Card Rack/Input File
The vehicle equipment, is mounted on the priority
vehicle. Its GPS receiver receives position
information from the constellation of GPS
satellites. This information is used to compute the
location, speed, and heading of the vehicle. This
information along with a priority request and the
state of the vehicle’s turn signal is broadcast using
the 2.4 GHz transceiver.
The intersection equipment receives this information.
The intersection equipment then compares the
information being received from the vehicle to the
parameters stored in the intersection equipment’s
memory. If the vehicle is heading towards the
intersection in a predefined approach corridor and is
requesting preemption and has met all other
programmed parameters, the corresponding phase
selector output is activated. This output is then
connected to the traffic controller preemption input.
When activated, the controller will then cycle to grant
a green light to the requesting vehicle or hold the
green allowing the vehicle to pass through the
intersection.
The card rack/input file provides the power and
logic wiring for the phase selector, which plugs
directly into a slot in the unit.
The auxiliary interface panel provides additional
connection for monitoring green phases and also
provides turn signal state dependent preemption
outputs.