1.2 - Provide Device Control DFD

This DFD shows the processes that make up the Provide Device Control facility within the Manage Traffic function. These processes provide the mechanism through which traffic management strategies can be implemented on the road and highway network served by the function.

The key points about this facility are as follows:

Traffic management provided through coordination of roadside equipment (indicators);
Traffic management strategy depends on current traffic conditions and default strategy;
Traffic management strategy can be overridden by Manage Incident and Manage Demand facilities;
Traffic management strategy can also be overridden by traffic operations personnel;
Indicators can be intersection, ramp or pedestrian controllers, or dynamic message signs (DMS);
Coordination of controller outputs can be based on a range of algorithms using real time data;
Controllers can operate using local data with no coordination;
Override strategies available to give emergency, high occupancy (HOV), and transit vehicle priority;
DMS can be used to guide drivers away from congestion and inform them of major incidents and alerts;
HAR can also be used to guide drivers away from congestion and inform them of major incidents and alerts;
DMS can also be used to guide drivers towards parking lots with spaces currently available;
Output of data to in-vehicle signage equipment provided through roadside units;
Output of environmental probe data collected from vehicles provided to other vehicles through roadside units;
Incorrect operation of indicators reported as faults to the maintenance and construction organization.

There are eight processes in this DFD, five of which are DFDs themselves:
a) Select Strategy (1.2.1)
b) Determine Road and Freeway State (DFD 1.2.2)
c) Determine Ramp State (1.2.3)
d) Output Control Data (DFD 1.2.4)
e) Manage Parking Lot (DFD 1.2.5)
f) Maintain Static Data for TMC (DFD 1.2.6)
g) Provide Roadside Control Facilities (DFD 1.2.7)
h) Collect Traffic Field Equipment Fault Data (1.2.8)

Although some of these processes depend on others in the group for data, they will each operate continuously and independently so that traffic control can be implemented in a timely fashion. Note that the processes in (g) receive data from the process (a) in the Provide Traffic Surveillance facility - see DFD 1.1, so that they can continue to function using local data if control data is not received from the processes in (d).

DFD: 1.2 - Provide Device Control

Parent DFD: 1 - Manage Traffic

Child DFDs:

PSpecs in this DFD: