< < TM19 : TM20 : TM21 > >

TM20: Variable Speed Limits

This service package sets variable speed limits along a roadway to create more uniform speeds, to promote safer driving during adverse conditions (such as fog), and/or to reduce air pollution. Also known as speed harmonization, this service monitors traffic and environmental conditions along the roadway. Based on the measured data, the system calculates and sets suitable speed limits, usually by lane. Equipment over and along the roadway displays the speed limits and additional information such as basic safety rules and current traffic information. The system can be centrally monitored and controlled by a traffic management center or it can be autonomous.

This service establishes variable speed limits and communicates the speed limits to drivers. Speed warnings and enforcement of speeds limits, including variable speed limits, is covered in the TM17-Speed Warning and Enforcement service package.

Variable speed limits are an Active Traffic Management (ATM) strategy and are typically used in conjunction with other ATM strategies (such as TM22-Dynamic Lane Management and Shoulder Use and TM23-Dynamic Roadway Warning).

Relevant Regions: Australia, Canada, European Union, and United States

Enterprise

Development Stage Roles and Relationships

Installation Stage Roles and Relationships

Operations Stage Roles and Relationships
(hide)

Source Destination Role/Relationship
ITS Roadway Equipment Manager ITS Roadway Equipment Manages
ITS Roadway Equipment Owner ITS Roadway Equipment Owns
ITS Roadway Equipment Owner ITS Roadway Equipment Manager Operations Agreement
ITS Roadway Equipment Owner Other ITS Roadway Equipment Owner Information Exchange and Action Agreement
ITS Roadway Equipment Owner Traffic Management Center Owner Information Exchange Agreement
ITS Roadway Equipment Supplier ITS Roadway Equipment Owner Warranty
Other ITS Roadway Equipment Manager Other ITS Roadway Equipment Manages
Other ITS Roadway Equipment Owner ITS Roadway Equipment Owner Information Exchange and Action Agreement
Other ITS Roadway Equipment Owner Other ITS Roadway Equipment Owns
Other ITS Roadway Equipment Owner Other ITS Roadway Equipment Manager Operations Agreement
Other ITS Roadway Equipment Supplier Other ITS Roadway Equipment Owner Warranty
Traffic Management Center Manager Traffic Management Center Manages
Traffic Management Center Manager Traffic Operations Personnel System Usage Agreement
Traffic Management Center Owner ITS Roadway Equipment Owner Information Exchange Agreement
Traffic Management Center Owner Traffic Management Center Owns
Traffic Management Center Owner Traffic Management Center Manager Operations Agreement
Traffic Management Center Supplier Traffic Management Center Owner Warranty
Traffic Operations Personnel Traffic Management Center Operates

Maintenance Stage Roles and Relationships

Functional

This service package includes the following Functional View PSpecs:

Physical Object Functional Object PSpec Number PSpec Name
ITS Roadway Equipment Roadway Basic Surveillance 1.1.1.1 Process Traffic Sensor Data
1.1.1.7 Process Road User Protection
1.1.2.11 Control Dynamic Lanes
1.2.7.16 Process Signal Control Conflict Monitoring
1.2.7.2 Monitor Roadside Equipment Operation
1.2.7.8 Provide Device Interface to Other Roadway Devices
1.3.1.3 Process Traffic Images
9.2.3.6 Collect Field Equipment Status for Repair
9.3.3.1 Collect Vehicle Speed
Roadway Environmental Monitoring 1.1.1.3 Process Environmental Sensor Data
1.2.7.1 Process Indicator Output Data for Roads
1.2.7.16 Process Signal Control Conflict Monitoring
1.2.7.2 Monitor Roadside Equipment Operation
1.2.7.8 Provide Device Interface to Other Roadway Devices
1.2.7.9 Process Roadway Information Data
9.2.3.6 Collect Field Equipment Status for Repair
9.3.3.1 Collect Vehicle Speed
Roadway Traffic Information Dissemination 1.2.7.1 Process Indicator Output Data for Roads
1.2.7.2 Monitor Roadside Equipment Operation
1.2.7.5 Process Indicator Output Data for Freeways
1.2.7.8 Provide Device Interface to Other Roadway Devices
1.2.7.9 Process Roadway Information Data
Roadway Variable Speed Limits 1.2.7.8 Provide Device Interface to Other Roadway Devices
1.2.7.9 Process Roadway Information Data
9.3.3.1 Collect Vehicle Speed
Traffic Management Center TMC Basic Surveillance 1.1.2.1 Process Traffic Data for Storage
1.1.2.2 Process Traffic Data
1.1.2.3 Update Data Source Static Data
1.1.2.5 Process Vehicle Situation Data
1.1.2.8 Process Roadway Environmental Data
1.1.3 Generate Predictive Traffic Model
1.1.4.1 Retrieve Traffic Data
1.1.4.2 Provide Traffic Operations Personnel Traffic Data Interface
1.1.5 Exchange Data with Other Traffic Centers
1.2.6.1 Maintain Traffic and Sensor Static Data
1.2.8 Collect Traffic Field Equipment Fault Data
1.3.1.1 Analyze Traffic Data for Incidents
1.3.2.1 Store Possible Incident Data
1.3.2.5 Provide Current Incidents Store Interface
1.3.2.6 Manage Traffic Routing
1.3.4.2 Provide Traffic Operations Personnel Incident Interface
1.3.4.5 Process Video Data
TMC Environmental Monitoring 1.1.2.5 Process Vehicle Situation Data
1.1.2.8 Process Roadway Environmental Data
1.1.4.1 Retrieve Traffic Data
1.1.4.2 Provide Traffic Operations Personnel Traffic Data Interface
1.1.4.4 Manage Traffic Archive Data
1.1.5 Exchange Data with Other Traffic Centers
1.2.4.3 Output In-vehicle Signage Data
1.2.4.7 Manage Roadway Warning System
1.2.8 Collect Traffic Field Equipment Fault Data
TMC Traffic Information Dissemination 1.1.4.1 Retrieve Traffic Data
1.1.4.2 Provide Traffic Operations Personnel Traffic Data Interface
1.1.4.3 Provide Direct Media Traffic Data Interface
1.2.1 Select Strategy
1.2.4.3 Output In-vehicle Signage Data
1.2.4.4 Output Roadway Information Data
1.2.8 Collect Traffic Field Equipment Fault Data
1.3.1.1 Analyze Traffic Data for Incidents
1.3.2.1 Store Possible Incident Data
1.3.2.2 Review and Classify Possible Incidents
1.3.2.5 Provide Current Incidents Store Interface
1.3.2.6 Manage Traffic Routing
1.3.4.2 Provide Traffic Operations Personnel Incident Interface
1.3.4.5 Process Video Data
TMC Variable Speed Limits 1.1.2.5 Process Vehicle Situation Data
1.1.2.8 Process Roadway Environmental Data
1.2.4.3 Output In-vehicle Signage Data
1.2.8 Collect Traffic Field Equipment Fault Data
1.3.1.1 Analyze Traffic Data for Incidents
1.3.2.5 Provide Current Incidents Store Interface
1.3.2.6 Manage Traffic Routing
9.3.3.3 Manage Vehicle Speed on Roadway

Physical

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Includes Physical Objects:

Physical Object Class Description
Driver Vehicle The 'Driver' represents the person that operates a vehicle on the roadway. Included are operators of private, transit, commercial, and emergency vehicles where the interactions are not particular to the type of vehicle (e.g., interactions supporting vehicle safety applications). The Driver originates driver requests and receives driver information that reflects the interactions which might be useful to all drivers, regardless of vehicle classification. Information and interactions which are unique to drivers of a specific vehicle type (e.g., fleet interactions with transit, commercial, or emergency vehicle drivers) are covered by separate objects.
ITS Roadway Equipment Field 'ITS Roadway Equipment' represents the ITS equipment that is distributed on and along the roadway that monitors and controls traffic and monitors and manages the roadway. This physical object 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 ramp metering systems. Lane management systems and barrier systems that control access to transportation infrastructure such as roadways, bridges and tunnels are also included. This object also provides environmental monitoring including sensors that measure road conditions, surface weather, and vehicle emissions. Work zone systems including work zone surveillance, traffic control, driver warning, and work crew safety systems are also included.
Other ITS Roadway Equipment Field Representing another set of ITS Roadway Equipment, 'Other ITS Roadway Equipment' supports 'field device' to 'field device' communication and coordination, and provides a source and destination for information that may be exchanged between ITS Roadway Equipment. The interface enables direct coordination between field equipment. Examples include the direct interface between sensors and other roadway devices (e.g., Dynamic Message Signs) and the direct interface between roadway devices (e.g., between a Signal System Master and Signal System Local equipment) or a connection between an arterial signal system master and a ramp meter controller.
Traffic Management Center Center The 'Traffic Management Center' monitors and controls traffic and the road network. It represents centers that manage a broad range of transportation facilities including freeway systems, rural and suburban highway systems, and urban and suburban traffic control systems. It communicates with ITS Roadway Equipment and Connected Vehicle Roadside Equipment (RSE) to monitor and manage traffic flow and monitor the condition of the roadway, surrounding environmental conditions, and field equipment status. It manages traffic and transportation resources to support allied agencies in responding to, and recovering from, incidents ranging from minor traffic incidents through major disasters.
Traffic Operations Personnel Center 'Traffic Operations Personnel' represents the people that operate a traffic management center. These personnel interact with traffic control systems, traffic surveillance systems, incident management systems, work zone management systems, and travel demand management systems. They provide operator data and command inputs to direct system operations to varying degrees depending on the type of system and the deployment scenario.

Includes Functional Objects:

Functional Object Description Physical Object
Roadway Basic Surveillance 'Roadway Basic Surveillance' monitors traffic conditions using fixed equipment such as loop detectors and CCTV cameras. ITS Roadway Equipment
Roadway Environmental Monitoring 'Roadway Environmental Monitoring' measures environmental conditions and communicates the collected information back to a center where it can be monitored and analyzed or to other field devices to support communications to vehicles. A broad array of weather and road surface information may be collected. Weather conditions that may be measured include temperature, wind, humidity, precipitation, and visibility. Surface and sub-surface sensors can measure road surface temperature, moisture, icing, salinity, and other metrics. ITS Roadway Equipment
Roadway Traffic Information Dissemination 'Roadway Traffic Information Dissemination' includes field elements that provide information to drivers, including dynamic message signs and highway advisory radios. ITS Roadway Equipment
Roadway Variable Speed Limits 'Roadway Variable Speed Limits' includes the field equipment, physical overhead lane signs and associated control electronics that are used to manage and control variable speed limits systems. This equipment monitors traffic and environmental conditions along the roadway. The system can be centrally monitored and controlled by a Traffic Management Center or it can be autonomous, calculating and setting suitable speed limits, usually by lane. This application displays the speed limits and additional information such as basic safety rules and current traffic information to drivers. ITS Roadway Equipment
TMC Basic Surveillance 'TMC Basic Surveillance' remotely monitors and controls traffic sensor systems and surveillance (e.g., CCTV) equipment, and collects, processes and stores the collected traffic data. Current traffic information and other real-time transportation information is also collected from other centers. The collected information is provided to traffic operations personnel and made available to other centers. Traffic Management Center
TMC Environmental Monitoring 'TMC Environmental Monitoring' assimilates current and forecast road conditions and surface weather information using a combination of weather service provider information, information collected by other centers such as the Maintenance and Construction Management Center, data collected from environmental sensors deployed on and about the roadway, and information collected from connected vehicles. The collected environmental information is monitored and presented to the operator. This information can be used to issue general traveler advisories and support location specific warnings to drivers. Traffic Management Center
TMC Traffic Information Dissemination 'TMC Traffic Information Dissemination' disseminates traffic and road conditions, closure and detour information, incident information, driver advisories, and other traffic-related data to other centers, the media, and driver information systems. It monitors and controls driver information system field equipment including dynamic message signs and highway advisory radio, managing dissemination of driver information through these systems. Traffic Management Center
TMC Variable Speed Limits 'TMC Variable Speed Limits' provides center monitoring and control of variable speed limits systems. It monitors data on traffic and environmental conditions collected from sensors along the roadway. Based on the measured data, it calculates and sets suitable speed limits usually by lane. It controls equipment that posts the current speed limits and displays additional information such as basic safety rules and current traffic information to drivers. Traffic Management Center

Includes Information Flows:

Information Flow Description
driver information Regulatory, warning, and guidance information provided to the driver while en route to support safe and efficient vehicle operation.
dynamic sign coordination The direct flow of information between field equipment. This includes information used to initialize, configure, and control dynamic message signs. This flow can provide message content and delivery attributes, local message store maintenance requests, control mode commands, status queries, and all other commands and associated parameters that support local management of these devices. Current operating status of dynamic message signs is returned.
environmental sensor coordination The direct flow of information between field equipment. This includes configuration and control of environmental sensors and the current road conditions (e.g., surface temperature, subsurface temperature, moisture, icing, treatment status) and surface weather conditions (e.g., air temperature, wind speed, precipitation, visibility) as measured and reported by fixed and/or mobile environmental sensors. Operational status of the sensors is also included.
environmental sensor data Current road conditions (e.g., surface temperature, subsurface temperature, moisture, icing, treatment status) and surface weather conditions (e.g., air temperature, wind speed, precipitation, visibility) as measured and reported by fixed and/or mobile environmental sensors. Operational status of the sensors is also included.
environmental sensors control Data used to configure and control environmental sensors.
roadway dynamic signage data Information used to initialize, configure, and control dynamic message signs. This flow can provide message content and delivery attributes, local message store maintenance requests, control mode commands, status queries, and all other commands and associated parameters that support remote management of these devices.
roadway dynamic signage status Current operating status of dynamic message signs.
traffic detector control Information used to configure and control traffic detector systems such as inductive loop detectors and machine vision sensors.
traffic detector coordination The direct flow of information between field equipment. This includes information used to configure and control traffic detector systems such as inductive loop detectors and machine vision sensors Raw and/or processed traffic detector data is returned that allows derivation of traffic flow variables (e.g., speed, volume, and density measures) and associated information (e.g., congestion, potential incidents). This flow includes the traffic data and the operational status of the traffic detectors
traffic detector data Raw and/or processed traffic detector data which allows derivation of traffic flow variables (e.g., speed, volume, and density measures) and associated information (e.g., congestion, potential incidents). This flow includes the traffic data and the operational status of the traffic detectors
traffic image meta data Meta data that describes traffic images. Traffic images (video) are in another flow.
traffic images High fidelity, real-time traffic images suitable for surveillance monitoring by the operator or for use in machine vision applications. This flow includes the images. Meta data that describes the images is contained in another flow.
traffic operator data Presentation of traffic operations data to the operator including traffic conditions, current operating status of field equipment, maintenance activity status, incident status, video images, security alerts, emergency response plan updates and other information. This data keeps the operator appraised of current road network status, provides feedback to the operator as traffic control actions are implemented, provides transportation security inputs, and supports review of historical data and preparation for future traffic operations activities.
traffic operator input User input from traffic operations personnel including requests for information, configuration changes, commands to adjust current traffic control strategies (e.g., adjust signal timing plans, change DMS messages), and other traffic operations data entry.
variable speed limit control Information used to configure and control variable speed limit systems including the equipment used to provide current speed limits and other information to drivers.
variable speed limit coordination The direct flow of information between field equipment. This includes information used to configure, control, and monitor variable speed limit systems including the equipment used to provide current speed limits and other information to drivers.
variable speed limit status Current operating status of the variable speed limit systems including the state of the equipment.
video surveillance control Information used to configure and control video surveillance systems.
video surveillance coordination The direct flow of information between field equipment. This includes information used to configure and control video surveillance systems and the high fidelity, real-time traffic images and associated meta data that are returned.

Goals and Objectives

Associated Planning Factors and Goals

Planning Factor Goal
A. Support the economic vitality of the metropolitan area, especially by enabling global competitiveness, productivity, and efficiency; Improve the national freight network, strengthen the ability of rural communities to access national and international trade markets, and support regional economic development
B. Increase the safety of the transportation system for motorized and nonmotorized users; Achieve a significant reduction in traffic fatalities and serious injuries on all public roads
D. Increase the accessibility and mobility of people and for freight; Achieve a significant reduction in congestion
G. Promote efficient system management and operation; Improve the efficiency of the surface transportation system
I. Improve the resiliency and reliability of the transportation system and reduce or mitigate stormwater impacts of surface transportation; Improve the resiliency and reliability of the surface transportation system

Associated Objective Categories

Objective Category
Freeway Management: Efficiency
Freeway Management: Reliability
Freight Management: Travel Time Reliability
Safety: Vehicle Crashes and Fatalities
Special Event Management: Entry/Exit Travel Times
System Efficiency: Cost of Congestion
System Efficiency: Delay
System Efficiency: Duration of Congestion
System Efficiency: Extent of Congestion
System Efficiency: Intensity of Congestion (Travel Time Index)
System Efficiency: Travel Time
System Reliability: Non-Recurring Delay
System Reliability: Planning Time Index
System Reliability: Travel Time 90th/95th Percentile
System Reliability: Travel Time Buffer Index
System Reliability: Variability

Associated Objectives and Performance Measures

Objective Performance Measure
Annual rate of change in regional average commute travel time will not exceed regional rate of population growth through the year Y. Average commute trip travel time (minutes).
Decrease the average buffer index for (multiple routes or trips) by X percent over Y years. The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).
Decrease the buffer index for (specific travel routes) by X percent over the next Y years. The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).
Improve average travel time during peak periods by X percent by year Y. Average travel time during peak periods (minutes).
Maintain the rate of growth in facility miles experiencing recurring congestion as less than the population growth rate (or employment growth rate). Percent of lane-miles (or rail) operating at LOS F or V/C > 1.0
Reduce average time to clear event's exiting queue by X percent in Y years. Average time to clear event's exiting queue by year per event.
Reduce average travel time into and out of the event by X percent in Y years. Average travel time away from selected special events to a set of locations over a year.
Reduce average travel time into and out of the event by X percent in Y years. Average travel time to selected special events from a set of locations in the area over a year.
Reduce buffer index on regional freight routes during peak and off-peak periods by X percent in Y years. Buffer Index on regional freight routes during peak and off-peak period.
Reduce buffer index on the freeway system during peak and off-peak periods by X percent in Y years. The buffer index (represents the extra time (buffer) travelers add to their average travel time when planning trips in order to arrive on-time 95 percent of the time).
Reduce buffer time index for travelers to multiple similar special events by X percent in Y years. Buffer time index for travelers to multiple similar special events.
Reduce crashes due to road weather conditions Number of crashes and fatalities related to weather conditions
Reduce crashes due to unexpected congestion Number of crashes and fatalities related to unexpected congestion
Reduce delay associated with incidents on the freeway system by X percent by year Y. Hours of delay associated with incidents.
Reduce hours of delay per capita by X percent by year Y. Hours of delay (person-hours).
Reduce hours of delay per capita by X percent by year Y. Hours of delay per capita.
Reduce hours of delay per driver by X percent by year Y. Hours of delay (person-hours).
Reduce hours of delay per driver by X percent by year Y. Hours of delay per driver.
Reduce lane departure crashes Number of crashes and fatalities related to inappropriate lane departure, crossing or merging
Reduce non-special event VMT in the event area during events by X percent in Y years. Non-special event VMT in the event area during events over a year.
Reduce secondary crashes Number of secondary crashes
Reduce speed differential Number of crashes and fatalities related to excessive speeding
Reduce speed differential Number of speed violations
Reduce the 90th (or 95th) percentile travel times for each route selected by X percent over Y years. 95th or 90th percentile travel times for selected routes.
Reduce the annual monetary cost of congestion per capita for the next X years. Cost (in dollars) of congestion or delay per capita.
Reduce the average buffer time needed to arrive on-time for 95 percent of trips on (specified routes) by X minutes over Y years. The buffer index represents the extra time (buffer) most travelers add to their average travel time when planning trips. This is the extra time between the average travel time and near-worst case travel time (95th percentile). The buffer index is stated as a percentage of the average travel time. Average buffer index or buffer time can be calculated using miles traveled as a weighting factor. Buffer time = 95th percentile travel time (min) – average travel time (min).
Reduce the average of the 90th (or 95th) percentile travel times for (a group of specific travel routes or trips in the region) by X minutes in Y years. 95th or 90th percentile travel times for selected routes.
Reduce the average planning time for (specific routes in region) by X minutes over the next Y years. The planning time index represents the time that must be added to travel time at free-flow speeds or the posted speed limit to ensure on time arrivals for 95 percent of the trips. Planning time = 95th percentile travel time (minutes) – Travel time at free-flow speed or posted speed limit. Average planning time index or planning time can be computed using a weighted average over person miles traveled.
Reduce the average planning time index for (specific routes in region) by X (no units) over the next Y years. The planning time index represents the time that must be added to travel time at free-flow speeds or the posted speed limit to ensure on time arrivals for 95 percent of the trips. Planning time = 95th percentile travel time (minutes) – Travel time at free-flow speed or posted speed limit. Average planning time index or planning time can be computed using a weighted average over person miles traveled.
Reduce the daily hours of recurring congestion on major freeways from X to Y by year Z. Hours per day at LOS F or V/C > 1.0 (or other threshold).
Reduce the number of hours per day that the top 20 most congested roadways experience recurring congestion by X percent by year Y. Hours per day at LOS F or V/C > 1.0 (or other threshold).
Reduce the number of pedestrian fatalities by X percent by year Y. Number of pedestrian fatalities
Reduce the number of person hours (or vehicle hours) of delay experienced by travelers on the freeway system. Hours of delay (vehicle-hours or person-hours).
Reduce the number of person hours (or vehicle hours) of delay experienced by travelers on the freeway system. Hours of delay per capita or driver.
Reduce the number of speeding-related fatalities by X percent by year Y. Number of speeding-related fatalities
Reduce the percentage of facility miles (highway, arterial, rail, etc.) experiencing recurring congestion during the peak period by X percent by year Y. Percent of lane-miles (or rail) operating at LOS F or V/C > 1.0
Reduce the rate fatalities in the region by X percent by year Y. Rate of fatalities (rate per vehicle miles travelled (VMT))
Reduce the rate of severe injuries in the region by X percent by year Y. Rate of serious injuries (rate per VMT)
Reduce the regional average travel time index by X percent per year. Travel time index (the average travel time during the peak period, using congested speeds, divided by the off-peak period travel time, using posted or free-flow speeds).
Reduce the share of freeway miles at Level of Service (LOS) X by Y by year Z. Miles at LOS X or V/C > 1.0 (or other threshold).
Reduce the share of major intersections operating at LOS Z by X percent by year Y. Percent of intersections operating at LOS F or V/C > 1.0
Reduce the total number of crashes in the region by X percent by year Y. Total crashes per X VMT.
Reduce the total number of fatalities and severe injuries in the region by X percent by year Y. Total fatalities per X VMT.
Reduce the total number of fatalities and severe injuries in the region by X percent by year Y. Total severe injuries per X VMT.
Reduce the total number of fatalities in the region by X percent by year Y. Number of fatalities
Reduce the total number of severe injuries in the region by X percent by year Y. Number of serious injuries
Reduce the variability of travel time on specified routes by X percent during peak and off-peak periods by year Y. Variance of travel time. Variance is the sum of the squared deviations from the mean. This can also be calculated as the standard deviation of travel time. Standard deviation is the square root of variance.
Reduce total person hours of delay (or travel-time delay per capita) by time period (peak, off-peak) caused by all transient events such as traffic incidents, special events, and work zones. Total person hours of delay during scheduled and/or unscheduled disruptions to travel.
Reduce total person hours of delay (or travel-time delay per capita) by time period (peak, off-peak) caused by scheduled events, work zones, or system maintenance by x hours in y years. Travel time delay during scheduled and/or unscheduled disruptions to travel.
Reduce total person hours of delay (or travel-time delay per capita) by time period (peak, off-peak) caused by unscheduled disruptions to travel. Total person hours of delay during scheduled and/or unscheduled disruptions to travel.


 
Since the mapping between objectives and service packages is not always straight-forward and often situation-dependent, these mappings should only be used as a starting point. Users should do their own analysis to identify the best service packages for their region.

Needs and Requirements

Need Functional Object Requirement
01 Traffic Operations need to be able to collect data from multiple sources to actively recommend variable speed limits which can be based on environmental conditions. Roadway Basic Surveillance 01 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.
02 The field element shall collect, process, and send traffic images to the center for further analysis and distribution.
Roadway Environmental Monitoring 01 The field element shall include surface and sub-surface environmental sensors that measure road surface temperature, moisture, icing, salinity, and other measures.
02 The field element shall include environmental sensors that measure weather conditions including temperature, wind, humidity, precipitation, and visibility.
10 The field element shall provide weather and road surface condition data to centers.
Roadway Variable Speed Limits 01 The field element shall monitor traffic and environmental conditions along the roadway.
06 The field element shall collect operational status of the variable speed limit field equipment and report the operational status to the controlling center.
07 The field element shall monitor and report faults to the controlling center.
TMC Basic Surveillance 01 The center shall monitor, analyze, and store traffic sensor data (speed, volume, occupancy) collected from field elements under remote control of the center.
02 The center shall monitor, analyze, and distribute traffic images from CCTV systems under remote control of the center.
07 The center shall remotely control devices to detect traffic.
TMC Environmental Monitoring 01 The traffic center shall remotely control environmental sensors that measure road surface conditions including temperature, moisture, icing, salinity, and other measures.
02 The traffic center shall remotely control environmental sensors that measure weather conditions including temperature, wind, humidity, precipitation, and visibility.
TMC Variable Speed Limits 01 The center shall monitor data on traffic and environmental conditions collected from sensors along the roadway.
03 The center shall control field equipment that posts the current speed limits and displays additional information such as basic safety rules and current traffic information to drivers.
04 The center shall monitor the operational status of the variable speed limit equipment, including fault reports.
02 Traffic Operations need to be able to process current and historical data in order to provide recommended variable speed limits. Roadway Variable Speed Limits 03 The field element shall receive commands from the controlling center that establish speed limits by lane.
04 The field element shall display the current speed limits per lane to drivers.
TMC Basic Surveillance 01 The center shall monitor, analyze, and store traffic sensor data (speed, volume, occupancy) collected from field elements under remote control of the center.
02 The center shall monitor, analyze, and distribute traffic images from CCTV systems under remote control of the center.
07 The center shall remotely control devices to detect traffic.
TMC Variable Speed Limits 02 Based on the measured data, the center shall calculate and set suitable speed limits by lane.
03 Traffic Operations need to be able to display variable speed limits to drivers. Roadway Traffic Information Dissemination 01 The field element shall include dynamic message 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).
03 The field element shall provide operational status for the driver information systems equipment (DMS, HAR, etc.) to the center.
04 The field element shall provide fault data for the driver information systems equipment (DMS, HAR, etc.) to the center for repair.
TMC Traffic Information Dissemination 03 The center shall collect operational status for the driver information systems equipment (DMS, HAR, etc.).
04 The center shall collect fault data for the driver information systems equipment (DMS, HAR, etc.) for repair.
TMC Variable Speed Limits 06 The center shall provide the current speed limits and additional information such as basic safety rules and current traffic information to drivers.

Related Sources

Document Name Version Publication Date
Concept of Operations for Road Weather Connected Vehicle Application Final 5/31/2013
Concept of Operations For Road Weather Connected Vehicle Applications Draft v1.4.2 6/26/2012
ITS User Services Document 1/1/2005


Security

In order to participate in this service package, each physical object should meet or exceed the following security levels.

Physical Object Security
Physical Object Confidentiality Integrity Availability Security Class
ITS Roadway Equipment Moderate Moderate Moderate Class 2
Other ITS Roadway Equipment Moderate Moderate Moderate Class 2
Traffic Management Center Moderate High Moderate Class 3



In order to participate in this service package, each information flow triple should meet or exceed the following security levels.

Information Flow Security
Source Destination Information Flow Confidentiality Integrity Availability
Basis Basis Basis
ITS Roadway Equipment Driver driver information Not Applicable High Moderate
This data is sent to all drivers and is also directly observable, by design. This is the primary signal trusted by the driver to decide whether to go through the intersection and what speed to go through the intersection at; if it's wrong, accidents could happen. If the lights are out you have to get a policeman to direct traffic – expensive and inefficient and may cause a cascading effect due to lack of coordination with other intersections.
ITS Roadway Equipment Other ITS Roadway Equipment dynamic sign coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
ITS Roadway Equipment Other ITS Roadway Equipment environmental sensor coordination Moderate Moderate Low
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
ITS Roadway Equipment Other ITS Roadway Equipment traffic detector coordination Moderate Moderate Low
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
ITS Roadway Equipment Other ITS Roadway Equipment variable speed limit coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
ITS Roadway Equipment Other ITS Roadway Equipment video surveillance coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
ITS Roadway Equipment Traffic Management Center environmental sensor data Low Moderate Moderate
Little to no impact if this data is observed info should be correct to determine safe speeds etc.; DISC: WYO believes this to be HIGH Updates are desireable but slightly outdated information will not be catastrophic.
ITS Roadway Equipment Traffic Management Center roadway dynamic signage status Moderate Moderate Moderate
Device status information should not be available, as those with criminal intent may use this information toward their own ends. Data is intended to feed dissemination channels, either C-ITS messages or DMS or other channels, so it should generally be correct as it is distributed widely and any forgery or corrupted data will have widespread impact. Failure of this flow affects traveler information dissemination, the importance of which varies with the data contained in the flow and the scenario. Could be LOW in many instances.
ITS Roadway Equipment Traffic Management Center traffic detector data Low Moderate Moderate
No impact if someone sees the data Some minimal guarantee of data integrity is necessary for all C-ITS flows. THEA believes this to be LOW.only limited adverse effect if raw/processed traffic detector data is bad/compromised; DISC: WYO believes this to be HIGH Only limited adverse effect of info is not timely/readily available, however without this information it will be difficult to perform traffic management activities, thus MODERATE. If not used for management, may be LOW.
ITS Roadway Equipment Traffic Management Center traffic image meta data Low Moderate Moderate
Traffic image data is generally intended for public consumption, and in any event is already video captured in the public arena, so this must be LOW. While accuracy of this data is important for decision making purposes, applications should be able to cfunction without it. Thus MODERATE generally. While accuracy of this data is important for decision making purposes, applications should be able to function without it. Thus MODERATE generally.
ITS Roadway Equipment Traffic Management Center traffic images Low Moderate Low
Traffic image data is generally intended for public consumption, and in any event is already video captured in the public arena, so this must be LOW. Generally transportation coordination information should be correct between source and destination, or inappropriate actions may be taken. While useful, there is no signficant impact if this flow is not available.
ITS Roadway Equipment Traffic Management Center variable speed limit status Low Moderate Moderate
This information is directly observable The TMC will react based on current status of ITS-RE and thus this information should be trusted. DISC: WYO believes this to be HIGH. The information should be available to ensure timely response from TMC
Other ITS Roadway Equipment ITS Roadway Equipment dynamic sign coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Other ITS Roadway Equipment ITS Roadway Equipment environmental sensor coordination Moderate Moderate Low
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Other ITS Roadway Equipment ITS Roadway Equipment traffic detector coordination Moderate Moderate Low
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Other ITS Roadway Equipment ITS Roadway Equipment variable speed limit coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Other ITS Roadway Equipment ITS Roadway Equipment video surveillance coordination Moderate Moderate Moderate
Any control flow has some confidentiality requirement, as observation of the flow may enable an attacker to analyze and learn how to assume control. MODERATE for most flows as the potential damage is likely contained, though anything that could have a significant safety impact may be assigned HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Since this directly impacts device control, we consider it the same as a control flow. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Traffic Management Center ITS Roadway Equipment environmental sensors control Moderate Moderate Low
Control flows, even for seemingly innocent devices, should be kept confidential to minimize attack vectors. While an individual installation may not be particularly impacted by a cyberattack of its sensor network, another installation might be severely impacted, and different installations are likely to use similar methods, so compromising one leads to compromising all. DISC: THEA, WYO believe this to be LOW: encrypted, authenticated, proprietary; but should not cause severe damage if seen Should be accurate and not be tampered with; could enable outside control of traffic sensors but should not cause severe harm, but could cause issues with environmental sensor data received and be detrimental to operations; DISC: WYO believes this may be HIGH for some applications Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH. From THEAwant updates but delayed information will not be severe; should be able to operate from a previous/default control/config; DISC: WYO believes this to be MODERATE
Traffic Management Center ITS Roadway Equipment roadway dynamic signage data Moderate Moderate Moderate
Device control information should not be available, as those with criminal intent may use this information toward their own ends. Data is intended to feed dissemination channels, either C-ITS messages or DMS or other channels, so it should generally be correct as it is distributed widely and any forgery or corrupted data will have widespread impact. Occasional outages of this flow will delay dissemination of the data to travelers (the eventual end user) which could have significant impacts on travel, both safety and mobility impacts.
Traffic Management Center ITS Roadway Equipment traffic detector control Moderate Moderate Low
Control flows, even for seemingly innocent devices, should be kept confidential to minimize attack vectors. While an individual installation may not be particularly impacted by a cyberattack of its sensor network, another installation might be severely impacted, and different installations are likely to use similar methods, so compromising one leads to compromising all. DISC: THEA, WYO believe this to be LOW: encrypted, authenticated, proprietary; but should not cause severe damage if seen Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH.. From THEA: should be accurate and not be tampered with; could enable outside control of traffic sensors but should not cause severe harm, but could cause issues with traffic sensor data received and be detrimental to operations Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.. From THEA: want updates but delayed information will not be severe; should be able to operate from a previous/default control/config. DISC: WYO believes this to be MODERATE
Traffic Management Center ITS Roadway Equipment variable speed limit control Moderate High Moderate
Control flows, even for seemingly innocent devices, should be kept confidential to minimize attack vectors. While an individual installation may not be particularly impacted by a cyberattack of its sensor network, another installation might be severely impacted, and different installations are likely to use similar methods, so compromising one leads to compromising all.. DISC: WYO believes this to be LOW or MODERATE depending on the application. NYC believes it to be LOW, as this information is directly observable. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. From NYC: The information sent from TMC directly affect the ITS-RE speed "announcement". NYC: The ITS-RE can work accordingly or in fail-safe if information is not available. WYO believes this to be MODERATE. Given the impacts for WYO scnearios, defaulted to MODERATE.
Traffic Management Center ITS Roadway Equipment video surveillance control Moderate Moderate Moderate
Control flows, even for seemingly innocent devices, should be kept confidential to minimize attack vectors. While an individual installation may not be particularly impacted by a cyberattack of its sensor network, another installation might be severely impacted, and different installations are likely to use similar methods, so compromising one leads to compromising all. Control flows, even for seemingly innocent devices, should have MODERATE integrity at minimum, just to guarantee that intended control messages are received. Incorrect, corrupted, intercepted and modified control messages can or will result in target field devices not behaving according to operator intent. The severity of this depends on the type of device, which is why some devices are set MODERATE and some HIGH. Control flow availability is related to the criticality of being able to remotely control the device. For most devices, this is MODERATE. For purely passive devices with no incident relationship, this will be LOW. All devices should have default modes that enable them to operate without backhaul connectivity, so no device warrants a HIGH.
Traffic Management Center Traffic Operations Personnel traffic operator data Moderate Moderate Moderate
Backoffice operations flows should have minimal protection from casual viewing, as otherwise imposters could gain illicit control or information that should not be generally available. Information presented to backoffice system operators must be consistent or the operator may perform actions that are not appropriate to the real situation. The backoffice system operator should have access to system operation. If this interface is down then control is effectively lost, as without feedback from the system the operator has no way of knowing what is the correct action to take.
Traffic Operations Personnel Traffic Management Center traffic operator input Moderate High High
Backoffice operations flows should have minimal protection from casual viewing, as otherwise imposters could gain illicit control or information that should not be generally available. Backoffice operations flows should generally be correct and available as these are the primary interface between operators and system. Backoffice operations flows should generally be correct and available as these are the primary interface between operators and system.

Standards

The following table lists the standards associated with physical objects in this service package. For standards related to interfaces, see the specific information flow triple pages.

Name Title Physical Object
ITE ATC Advanced Transportation Controller ITS Roadway Equipment
ITE ATC API Application Programming Interface Standard for the Advanced Transportation Controller ITS Roadway Equipment
ITE ATC ITS Cabinet Intelligent Transportation System Standard Specification for Roadside Cabinets ITS Roadway Equipment
ITE ATC Model 2070 Model 2070 Controller Standard ITS Roadway Equipment
NEMA TS 8 Cyber and Physical Security Cyber and Physical Security for Intelligent Transportation Systems ITS Roadway Equipment
Traffic Management Center
NEMA TS2 Traffic Controller Assemblies Traffic Controller Assemblies with NTCIP Requirements ITS Roadway Equipment
NEMA TS4 Hardware Standards for DMS Hardware Standards for Dynamic Message Signs (DMS) With NTCIP Requirements ITS Roadway Equipment