TxDOT District 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: Field Barrier System Control

Field elements that control barrier systems such as gates and other systems that manage entry to roadways, transportation facilities and infrastructure.

Functional Area: Roadway Automated Vehicle Operations

Automated Highway Systems (AHS) in the field that verify vehicle eligibility for AHS lane use, and control AHS check-in/out and lane-changing.

ID Requirement Status
1 The field element shall check the vehicle's condition to see if it is suitable for operating on automated lanes based on vehicle control parameters (speed, headway, etc.) used by vehicles in those lanes, and once confirmed, shall send control parameters to the vehicle. Long-term
2 The field element shall provide to the vehicle automated lane changing data based on a lane changing strategy and detailed lane changing parameters (e.g. exactly where, and at what speed the lane change will take place), under center control. Long-term
3 The field element shall manage the checking in and checking out of suitably equipped vehicles requesting use of automated lanes, and send a record of all requests to the responsible center. Long-term

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
3 The field element shall collect, digitize, and send multimodal crossing and high occupancy vehicle (HOV) lane sensor data to the center for further analysis and storage. Long-term
4 The field element shall return sensor and CCTV system operational status to the controlling center. Existing
5 The field element shall return sensor and CCTV system fault data to the controlling center for repair. Existing

Functional Area: Roadway Dynamic Lane Management and Shoulder Use

Field elements including physical overhead lane signs and associated control electronics that are used to manage and control specific lanes, including temporary use of shoulders as travel lanes.

ID Requirement Status
1 The field element shall measure traffic conditions per lane, under center control. Long-term
2 The field element shall determine how to change the lane controls to respond to current traffic and road conditions. Long-term
3 The field element shall receive lane management control information from the controlling center. Long-term
4 The field element shall provide guidance and information to drivers regarding current lane configuration and status. Long-term
5 The field element shall monitor vehicle characteristics and classify individual vehicles. Long-term
7 The field element shall monitor current lane usage to determine if vehicles are complying with current lane use restrictions. Long-term
8 The field element shall capture vehicle information, including vehicle image(s) of vehicles violating current lane usage restrictions and report violations to the controlling center. Long-term

Functional Area: Roadway Environmental Monitoring

Environmental sensors, surface and sub-surface, that collect weather and road surface information. Weather conditions measured include temperature, wind, humidity, precipitation, and visibility. Sensors measure road surface temperature, moisture, icing, salinity, etc.

ID Requirement Status
1 The field element shall include surface and sub-surface environmental sensors that measure road surface temperature, moisture, icing, salinity, and other measures. Medium-term
2 The field element shall include environmental sensors that measure weather conditions including temperature, wind, humidity, precipitation, and visibility. Existing
3 The field element's environmental sensors shall be remotely controlled by a maintenance center. Medium-term
4 The field element's environmental sensors shall be remotely controlled by a traffic management center. Existing
7 The field element shall provide environmental sensor equipment operational status to the controlling center or maintenance vehicle. Medium-term
8 The field element shall provide environmental sensor equipment fault indication to the controlling center or maintenance vehicle. Existing
9 The field element shall remotely aggregate environmental sensor data with environmental data collected from maintenance and construction vehicles. Medium-term
10 The field element shall provide weather and road surface condition data to centers. Existing

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.

ID Requirement Status
1 The field element shall include sensors that provide data and status information to other field element devices, without center control. Existing
2 The field element shall include sensors that receive configuration data from other field element devices, without center control. Existing
3 The field element shall include devices that provide data and status information to other field element devices without center control. Existing
4 The field element shall include devices that receive configuration data from other field element devices, without center control. Existing

Functional Area: Roadway Field Device Monitoring

Monitors field equipment operational status and detects and reports fault conditions. Device status, configuration, and fault information are provided to a remote center and a user interface provides information locally to field personnel.

ID Requirement Status
1 The field element shall monitor the operational status (state of the device, configuration, and fault data) of connected sensors (such as traffic, infrastructure, environmental, security, speed) and devices (such as highway advisory radio, dynamic message signs, automated roadway treatment systems, barrier and safeguard systems, cameras, traffic signals, ramp meters, short range communications equipment, security surveillance equipment). Medium-term
2 The field element shall send operational status of connected field equipment to the maintenance center. Medium-term
3 The field element shall send collected fault data to the maintenance center for repair. Medium-term
4 The field element shall include a local interface that provides operational status and fault data for connected field equipment to field personnel. Medium-term
5 The field element shall include a local interface that allows field personnel to command diagnostic tests on connected field equipment. Medium-term

Functional Area: Roadway HOV Control

HOV lane usage traffic sensors and display equipment to notify users of HOV lane status for control of traffic in HOV lanes on freeways.

ID Requirement Status
1 The field element shall include sensors to detect high-occupancy vehicle (HOV) lane usage, under center control. Existing
2 The field element shall include driver information systems to notify users of lane status for lanes that become HOV or High Occupancy Toll (HOT) lanes during certain times of the day on freeways, under center control. Existing
3 The field element shall include freeway control devices, such as ramp signals and mainline metering and other systems associated with freeway operations that control use of HOV lanes, under center control. Existing
5 The field element shall provide traffic flow measures and information regarding vehicle occupancy (i.e., lane usage) in HOV lanes to the center. Long-term
6 The field element shall return operational status for the HOV lane sensors 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
2 The field element shall remotely process video data and provide an indication of potential incidents to the traffic management center. Existing
3 The field element's video devices shall be remotely controlled by a traffic management center. Existing
4 The field element shall provide operational status and fault data for the incident detection devices to the traffic management center. Existing

Functional Area: Roadway Intersection Safety Warning

Field elements that determine the probability of a collision in an intersection or at a railroad crossing and inform approaching vehicles using short-range wireless communications to the vehicles and traffic signal controls.

ID Requirement Status
1 The field element shall utilize traffic sensors to monitor vehicles approaching and occupying an intersection. Long-term
2 The field element shall monitor the operational state, signal timing, and current phase of the traffic signal. Long-term
3 The field element shall monitor road conditions on approaches to, and within, the intersection. Long-term
4 The field element shall communicate with approaching vehicles to determine vehicle position, velocity, acceleration, direction, and intended turning movement. Long-term
5 The field element shall detect potentially hazardous conditions including impending red-light or stop sign violations and potential conflicts between approaching vehicles. Long-term
6 The field element shall provide intersection status and warnings to approaching vehicles using field-vehicle communications. Long-term
7 The field element shall update signs or signals to warn the driver of potentially hazardous situations. Long-term

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
2 The field element shall include driver information systems that communicate directly from a center to the vehicle radio (such as Highway Advisory Radios) for dissemination of traffic and other information to drivers, under center control. Long-term
4 The field element shall provide operational status for the driver information systems equipment (DMS, HAR, etc.) to the center. Existing
5 The field element shall provide fault data for the driver information systems equipment (DMS, HAR, etc.) to the center for repair. Existing

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. Long-term
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. Long-term
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. Long-term

Functional Area: Roadway Variable Speed Limits

Field elements including physical overhead lane signs and associated monitoring, communications, and control electronics that are used to manage and control variable speed limits systems.

ID Requirement Status
3 The field element shall receive commands from the controlling center that establish speed limits by lane. Long-term
4 The field element shall display the current speed limits per lane to drivers. Long-term
5 The field element shall display additional information such as basic safety rules and current traffic information to drivers. Long-term
6 The field element shall collect operational status of the variable speed limit field equipment and report the operational status to the controlling center. Long-term
7 The field element shall monitor and report faults to the controlling center. Long-term

Functional Area: Roadway Warning

Field elements used to warn drivers approaching hazards including adverse road weather conditions, traffic conditions including queues, and obstacles or animals in the road.

ID Requirement Status
3 The field element shall monitor for debris, animals, or other objects in the travel lanes. Existing
5 The field element shall autonomously identify potentially hazardous conditions and activate warning signs to approaching motorists. Existing

Functional Area: Roadway Work Zone Safety

Work zone intrusion detection devices (to detect vehicle intrusion upon a work zone or crew worker movement across a work zone boundary) and intrusion alerting devices that provide alerts to crew and drivers.

ID Requirement Status
1 The field element shall include work zone intrusion detection devices that detect when a vehicle has intruded upon the boundary of a work zone, under center control. Medium-term
2 The field element shall include work zone intrusion detection devices that detect when crew workers have crossed the boundary between the work zone and vehicle traffic, under center control. Medium-term
3 The field element shall include work zone intrusion alerting devices that alert crew workers of a work zone emergency or safety issue such as the intrusion of a vehicle into the work zone area or movement of field crew into the travel lanes. Medium-term
4 The field element shall include work zone intrusion alerting devices that notify crew via maintenance vehicles of a work zone emergency or safety issue such as the intrusion of a vehicle into the work zone area or movement of field crew into the travel lanes. Medium-term
5 The field element shall include work zone intrusion alerting devices that alert drivers that they have intruded upon the perimeter of the work zone, or are about to do so; may provide alerts to drivers directly or via in-vehicle signing. Medium-term
6 The field element shall provide operational status for the work zone intrusion detection devices to the maintenance center. Medium-term
7 The field element shall provide fault data for the work zone intrusion detection devices to the maintenance center for repair. Medium-term
8 The field element shall provide operational status for the work zone intrusion alerting devices to the maintenance center. Medium-term
9 The field element shall provide fault data for the work zone intrusion alerting devices to the maintenance center for repair. Medium-term

Functional Area: Roadway Work Zone Traffic Control

Field elements in maintenance and construction areas including CCTV cameras, driver information systems (such as DMS), and gates/barriers that monitor and control traffic and provide information directly to drivers in affected areas.

ID Requirement Status
1 The field element shall collect, process, and send work zone images to the center for further analysis and distribution, under center control. Medium-term
2 Under traffic and maintenance center control, the field element shall include driver information systems (such as dynamic messages signs and highway advisory radios) that advise drivers of activity around the work zone through which they are currently passing. Medium-term
3 Under the control of field personnel within maintenance vehicles, the field element shall include driver information systems (such as dynamic messages signs and highway advisory radios) that advise drivers of activity around a work zone through which they are currently passing. Medium-term
4 The field element shall control access to the work zone using automated gate or barrier systems. This includes automated flagger assistance devices that include automated gate arms and other automated gate/barrier systems. Medium-term
5 The field element shall provide operational status for the surveillance (e.g. CCTV), driver information systems, and gates/barriers in work zones to the maintenance center. Medium-term
6 The field element shall provide fault data for the surveillance (e.g. CCTV), driver information systems, and gates/barriers in work zones to the maintenance center for repair. Medium-term