North Texas Tollway Authority Roadway Devices - Roadway Functionality

Subsystem Description

The Roadway Subsystem (RS) includes the equipment distributed on and along the roadway that monitors and controls traffic and monitors and manages the roadway itself. Equipment includes traffic detectors, environmental sensors, traffic signals, highway advisory radios, dynamic message signs, CCTV cameras and video image processing systems, grade crossing warning systems, and freeway ramp metering systems. HOV lane management, reversible lane management functions, and barrier systems that control access to transportation infrastructure such as roadways, bridges and tunnels are also supported. This subsystem also provides the capability for environmental monitoring including sensors that measure road conditions, surface weather, and vehicle emissions. In adverse conditions, automated systems can be used to apply anti-icing materials, disperse fog, etc. Work zone systems including work zone surveillance, traffic control, driver warning, and work crew safety systems are also included. To enhance security, safeguard systems such as blast shields, exhaust systems and other automated and remotely controlled systems to protect transportation infrastructure is also provided. In advanced implementations, this subsystem supports automated vehicle safety systems by safely controlling access to and egress from an Automated Highway System through monitoring of, and communications with, AHS vehicles. Intersection collision avoidance functions are provided by determining the probability of a collision in the intersection and sending appropriate warnings and/or control actions to the approaching vehicles.

Functional Area: Roadway Basic Surveillance

Field elements that monitor traffic conditions using loop detectors and CCTV cameras.

ID Requirement Status
1 The field element shall collect, process, digitize, and send traffic sensor data (speed, volume, and occupancy) to the center for further analysis and storage, under center control. Existing
2 The field element shall collect, process, and send traffic images to the center for further analysis and distribution. Existing
4 The field element shall return sensor and CCTV system operational status to the controlling center. Existing

Functional Area: Roadway Incident Detection

Field elements that monitor traffic conditions to identify incidents. It includes traffic detectors that collect traffic flow information and identify unusual traffic conditions and advanced CCTV cameras with built-in incident detection algorithms.

ID Requirement Status
1 The field element shall collect, process, and send traffic images to the center for further analysis and distribution. Existing
3 The field element's video devices shall be remotely controlled by a traffic management center. Existing

Functional Area: Roadway Signal Controls

Field elements including traffic signal controllers for use at signalized intersections; also supports pedestrian crossings.

ID Requirement Status
1 The field element shall control traffic signals under center control. Existing
4 The field element shall report the current signal control information to the center. Existing
6 The field element shall return traffic signal controller operational status to the center. Existing
7 The field element shall return traffic signal controller fault data to the center. Existing

Functional Area: Roadway Traffic Information Dissemination

Driver information systems, such as dynamic message signs and Highway Advisory Radio (HAR).

ID Requirement Status
1 The field element shall include dynamic messages signs for dissemination of traffic and other information to drivers, under center control; the DMS may be either those that display variable text messages, or those that have fixed format display(s) (e.g. vehicle restrictions, or lane open/close). Existing
4 The field element shall provide operational status for the driver information systems equipment (DMS, HAR, etc.) to the center. Existing