| Word |
Description |
| Decector Failures |
The occurrence of detector malfunctions including non-operation, chattering, or other intermittently erroneous detections. |
| Delayed Call Detector |
A detector that does not issue an output until the detection zone has been occupied for a period of time that exceeds the time preset on an adjustable timer incorporated into the detector unit. |
| Delayed Output |
The ability of a detector to delay its output for a predetermined length of time during an extended actuation (NEMA). |
| Delta L (L) |
The change in inductance. |
| Demand |
The request for service, e.g., one or more vehicles desiring to use a given segment of roadway during a specific unit of time. |
| Demand Control |
See Loop Occupancy Control |
| Demand Operation |
A mode of operation whereby the service provided at an intersection reflects the presence of deamand for that service without regard to the background cycles. |
| Density |
A measure of the concentration of vehicles, stated as the number of vehicles per mile per lane. |
| Density Controller |
Actuated controller that has timing adjustments for the selection of the allowable gap independent of the passage of time. A volume-density controller and a modified density controller are each a type of density controller. |
| Design Speed |
The speed used as typical by the designer of the detector/controller system in the kinematic analysis of the scheme under free traffic flow conditions. |
| Detection Zone |
That area of roadway within which a vehicle will be detected by a vehicle detector (NEMA). Also called "zone of detection" or "sensing zone". |
| Detector |
A device for indicating the presence of passage of vehicles or pedestrians (NEMA). This general term is usually supplemented with a modifier indicating type (e.g., loop detector, magnetic detector, etc.); operation (e.g., point detector, presence detector, etc.); or function (e.g., calling detector, extension detector, etc.). |
| Detector Amplifier |
A device that is capable of intensifying the electrical energy produce by a sensor (NEMAN).
An example is a magnetic detector amplifier. A loop detector unit is commonly call an amplifier, although its electronic function actually is different. |
| Detector Memory |
The retention of an actuation of future utilization by the controller assembly. The phrase might better be detection memory to make is clearer that the memory is within the controller, not the detector. |
| Detector Mode |
A term used to describe the operation off a detector channel output when a presence detection occurs (NEMA). See Pulse Mode, Controlled Output, Continuous Presence Mode, and Limited Presence Mode. |
| Detector Setback |
Longitudinal distance between stop line and detector. |
| Detector System |
The complete sensing and indication group consisting of the detector unit in the controller, the lead-in cable, the lead-in wires, and the sensor. |
| Detector Unit |
The portion of a detector system other that the sensor and lead-in cable, consisting of an electronic assembly. |
| Dielectric |
Any insulation material that is nonconductor of electricity. |
| Digi One |
The Digi One IA delivers efficient serial-to-Ethernet connectivity and is ideal for applications where TCP Socket, UDP Socket, or UDP multicast functionality is needed.
The Digi One IA terminal server allows any industrial device with a serial port to be connected to Ethernet. Digi One IA delivers cost-effective performance and capability in a rugged DIN Rail mountable enclosure specifically designed for the Industrial Automation market. |
| Dilemma Zone |
A distance or time interval related to the onset of the yellow interval. Originally used to describe that portion of the roadway in advance of the intersection within which a driver can neither stop prior to the stop line nor clear of the intersection before conflicting traffic is released.
More recently the term has been used to describe that portion of the roadway in advance of the intersection within which a driver is indecisive regarding stopping prior to the stop line or proceeding into or through the intersection.
Also may be expressed as the increment of time corresponding to the dilemma zone distance. |
| Dilemma-Zone Protection |
Any method or procedure that attempts to control the end of the green interval so that no vehicle will be caught in the dilemma zone when the signal turns yellow. |
| Direct Current (DC) |
An electrical current which travels uniformly in one direction. |
| Drift |
Change in the electrical properties of the detector system or portion of it due to environmental changes particularly temperature variations and rain water. |
| DVDT |
Daily Vehicle Distance Traveled |
