Caltrans D6 Ramp Meters - 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. | Planned |
| 4 | The field element shall return sensor and CCTV system operational status to the controlling center. | Planned |
| 5 | The field element shall return sensor and CCTV system fault data to the controlling center for repair. | Planned |
Functional Area: Roadway Equipment Coordination
Field elements that control and send data to other field elements (such as environmental sensors that send data to a DMS or coordination between traffic controllers on adjacent intersections), without center control.
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.
Functional Area: Roadway Traffic Information Dissemination
Driver information systems, such as dynamic message signs and Highway Advisory Radio (HAR).
Functional Area: Roadway Traffic Metering
Control equipment including ramp, interchange, and mainline meters and the dynamic message signs that provide information about the meters and any special bypass lanes.
| ID | Requirement | Status |
|---|---|---|
| 1 | The field element shall regulate the flow of traffic on ramps, interchanges, and the mainline, under center control. | Planned |
| 2 | The field element shall monitor operation of ramp, interchange, and mainline meters and report to the center any conflicts between received control plans and current system operation. | Planned |
| 3 | The field element shall return ramp, interchange, and mainline meter operational status to the controlling center. | Planned |
| 4 | The field element shall provide indications to the driver that the metering system is active and provide safe transitions between active and inactive status. | Planned |
| 5 | The field element shall return ramp, interchange, and mainline meter fault data to the maintenance center for repair. | Planned |