U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content
Facebook iconYouTube iconTwitter iconFlickr iconLinkedInInstagram

Safety

FHWA Home / Safety / Intersection / Advanced Dilemma-Zone Detection System

Advanced Dilemma-Zone Detection System

Detailed Description of Figures

Figure 1: Advanced Dilemma-Zone Detection system components as applied in TxDOT Detection-Control System study referenced in this fact sheet

Diagram shows that the vehicle detection system detects vehicles, then sends a signal to detector amplifiers, which transmits the data to an industrial personal computer (dimensions 7 inches by 7 inches by 10 inches), which then sends data to the digital input/output interface. From here, direction is sent to the traffic control system via a signal controller, which controls the signal head. Conflicting call signals are sent back to the digital input/output interface for decisionmaking to force or hold the signal.

Return to Figure 1.


Figure 2: Advanced Dilemma-Zone Detection design as applied in TxDOT Detection-Control System study

Diagram shows the positioning of an advanced dilemma-zone detection system on a roadway. On the approach to a signalized intersection, a D-CS Detector trap is set approximately 800 to 1,000 feet from the stop line. Segment A is furthest from the intersection and defines the dilemma zone of a vehicle traveling at 70 mph. Segment B is on the approach to an intersection and defines the dilemma zone of a vehicle traveling at 25 mph. Located right before the stop bar are stop line detectors in each lane at the intersection.

Return to Figure 2.

Page last modified on September 4, 2014
Safe Roads for a Safer Future - Investment in roadway safety saves lives
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000