• Introduction
• What are Weather-related Traveler
  Information Dissemination Systems?
• The Rationale for Weather-related
  Traveler Information Dissemination Systems
• System Description
  • Road Weather Information Systems (RWIS)
  • Additional Components of Weather-related
    Traveler Information Dissemination Systems
  • How are Weather-related Traveler Information
    Dissemination Systems Integrated with other ITS Weather Systems?
• Assessment
  • Key Results
  • Benefits
  • Costs
  • Implementation and Operational Challenges
• Where are Weather-related Traveler
  Information Dissemination Systems Implemented?
• Case Studies
• References

INTRODUCTION

What are Weather-related Traveler Information Dissemination Systems?

Weather-related traveler information systems can disseminate road weather information to highway agencies and travelers. Cellular or wireless phones, Highway Advisory Radio (HAR), Road Weather Information Systems (RWIS), Advanced Traveler Information Systems (ATIS), roadside displays, audio communication, Variable Message Signs (VMS), and internet sites are all systems used to disseminate traveler information. These systems often operate within larger information systems or state-run programs, which can in turn include other ITS weather-related technologies. For example, most traveler information systems also have weather detection and/or forecasting capabilities. Others can detect weather, forecast weather, and initiate road maintenance. Still others can detect weather, forecast weather, and control traffic in adverse weather conditions.

Traveler information systems can disseminate weather information to a variety of road users:

• Commuters
• Truckers
• Travelers
• Recreational travelers
• Highway agencies and personnel

The Rationale for Weather-related Traveler Information Dissemination Systems

Between 10% and 13% of all fatal US highway traffic deaths occur due to adverse weather, and most multiple vehicle pile-ups in past years have been triggered by ice, snow, blowing snow, or fog. When road users are more informed of upcoming road weather conditions, they are better prepared to respond accordingly (i.e. change travel route, adjust vehicle speed etc). Similarly, when road maintenance personnel are aware of forthcoming weather, they can make more informed decisions about how to deploy maintenance equipment and direct traffic flow.

SYSTEM DESCRIPTION

There are various types of weather-related traveler information dissemination systems and programs in the United States. While many of these systems or programs are specific to particular states, Road Weather Information Systems (RWIS) are the most widely used and operate on a nationwide level (see "Case Studies" for full descriptions of other Weather-related Traveler Information Programs).

Road Weather Information Systems (RWIS)

RWIS collect and transmit information about weather conditions to highway agencies and travelers. A RWIS uses historic and current climatological data to develop real-time road and weather information (i.e. forecasts). RWIS use specialized equipment and computer programs to monitor air and pavement temperatures in order to predict whether precipitation will freeze on the pavement. Sensors collect real-time data on air and pavement temperatures, precipitation, and the amount of deicing chemicals on the pavement. These are combined with information from meteorological services to predict pavement temperatures for a specific area, such as a mountain pass, over a 24-hour period. These predictions are then transmitted to a computer at the highway agency's winter maintenance center. This information is critical to an effective anti-icing strategy, since deicing chemicals must be applied about an hour before the pavement reaches freezing temperatures. This prevents ice from forming on the pavement, in contrast to traditional methods in which the ice is cleared after it has already bonded to the pavement. Using portable computers linked by modem to the central computer, maintenance managers can monitor conditions, advise motorists, and dispatch crews as necessary.

Here is an illustration of how information dissemination aids in the road maintenance decision-making process:

Source: Davies, Peter. Integrating ITS and Advanced Weather Prediction. ITS America. New thinking in transportation: conference proceedings. 1999.

RWIS include the following programs:

FORETELL
FORETELL collects, forecasts, and distributes highly specific road weather information that is pertinent to highway and trucking professionals, transit operators, everyday commuters, long-distance travelers, and all other road users. FORETELL is a multi-state initiative covering the Upper Mississippi Valley region funded in part by the Federal Highway Administration (FHWA). The mission of the FORETELL field operational test is to create a Road Weather Information System (RWIS) fully integrated within a wider set of Intelligent Transportation System (ITS) services to enhance safety and facilitate travel throughout North America. Information provided by this system will be disseminated to the Iowa DOT and eventually be made available to other agencies and to the public via a variety of technologies such as Highway Advisory Radio, Variable Message Signs and the Internet.

rWeather
The Washington State Department of Transportation (WSDOT) has undertaken development of rWeather, a real-time statewide system that collects and disseminates road and weather information. The web site provides access to real-time data from approximately 350 weather stations, traffic surveillance cameras, and mountain pass reports (during winter season) across the state. This application is currently being operated as a prototype.

Aurora
Aurora is a long-term program of collaborative research, development, and deployment of advanced technologies for detailed road and weather monitoring and forecasting. Aurora programs integrate road and weather technologies with weather monitoring infrastructures in order to forecast weather and provide real-time information to travelers. There are currently 5 completed Aurora projects and 16 on-going projects.

Advanced Traveler Information System (ATIS)
ATIS have many en-route guidance capabilities, one of which is to receive input about weather conditions and disseminate the information to travelers via commercial TV and radio, HAR, VMS, computer kiosks, telephones, and the internet.

Additional Components of Weather-related Traveler Information Dissemination Systems

• Cellular or wireless phones are used in programs like the Advanced Transportation Weather Information System (ATWIS), where travelers can call a designated traffic weather information number and receive updates on weather forecasts.
• Highway Advisory Radio (HAR) only broadcasts traffic and weather information and gives detailed weather information about specific areas.
• Variable Message Signs (VMS) alert drivers of upcoming road hazards due to inclement weather.

How are Weather-related Traveler Information Dissemination Systems Integrated with other ITS Weather Systems?

Most traveler information systems are integrated with other ITS weather systems in order to increase their efficiency. Here are examples of programs that illustrate these various combinations:

Traveler information systems that also detect weather:

The FHWA’s Highway Fog Warning System detects fog conditions with visibility sensors and conveys that information to drivers through roadside displays or audio communication.

Traveler information systems that also forecast weather:

Advanced Traveler Weather Information Systems (ATWIS) forecast weather conditions and provide travelers with road condition reports via cellular or wireless phones.

Traveler information systems that can detect and forecast weather:

Aurora research programs study the different aspects of RWIS, including ways of improving its forecasting and information dissemination capabilities.

Traveler information systems that can detect weather, forecast weather, and initiate road maintenance:

Anti-icing and de-icing technologies are often used in conjunction with RWIS, resulting in an integrated system that can forecast and monitor weather, maintain roads, and disseminate road weather information to travelers.

Traveler information systems that can detect weather, forecast weather, and control traffic in adverse weather conditions:

The Tennessee Fog Detection and Warning System detects foggy conditions, predicts fog formation, and disseminates this information to travelers via HAR and VMS. It also controls traffic speed through variable speed limit signs (VSL).

ASSESSMENT

Key Results

• RWIS are very effective at monitoring and forecasting weather as well as disseminating weather information to travelers and highway agencies.
• RWIS can provide information about specific trouble areas (i.e. intersections).
• VMS, HAR, and commercial radio are the most popular information dissemination systems.
• Information about road conditions that inhibit vehicle performance are most important to road users.
• Different road users need different kinds of information at different times.
• Truckers prefer to receive road weather information 3 hours prior to their trip, whereas recreational travelers prefer to receive this information en-route.
• All drivers prefer to receive information about road conditions and alternate routes than travel times and travel speeds.

Benefits

• Highway officials can make more informed choices about how to manage road networks in adverse weather conditions (i.e. how and when to deploy highway maintenance vehicles to treat roads affected by precipitation).
• All road users will know about upcoming weather conditions and can adjust their travel time, mode of transportation, or even delay their trip.

Costs

• RWIS: Capital Cost: 25k, Operation and Maintenance: 0.4-2.5k per year
• VMS: Capital Cost: 10-50k, Operation and Maintenance: 1.9-4.1k per year
• HAR: Capital Cost: 16-32k, Operation and Maintenance: 0.6-1k per year
• Informational Kiosk: Capital Cost: 9.55-50k, Operation and Maintenance: 0.955-5k per year

Implementation and Operational Challenges

• Nationwide RWIS need to be expandable, transferable, and compatible. The lack of a standardized architecture hinders the spread of RWIS.
• Many road maintenance staff are resistant to RWIS because they are uncomfortable with the new technologies and lack an understanding of their customers’ needs.
• Highway officials often provide overly conservative information about weather conditions, which can be misleading.
• Most state DOTs must go through the slow and inefficient processes of consulting numerous weather sources and interpreting weather data.
• More specific forecasts are needed so that forecasts can be integrated along particular travel routes.
• There should be more of a focus on measuring road surface temperatures, rather than atmospheric conditions, in order to provide travelers with more precise information.
• There is an on-going challenge to provide travelers with timely road weather information in a clear, accessible format.
• Different road user needs should be identified in order to provide them with relevant information.

WHERE ARE WEATHER-RELATED TRAVELER INFORMATION SYSTEMS IMPLEMENTED?

• ATWIS: North Dakota
• FORETELL: across the United States
• Aurora: worldwide
• SAFE-PASSAGE: Illinois and Washington
• RWIS: across the United States
• Tennessee Fog Detection and Warning System: Tennessee
• Anti-ice/De-ice: across the United States
• Snow Removal: across the United States
• MDSS: across the United States
• Mobile Road Condition Sensor Project: across the United States
• Fog Mitigation System: South Carolina
• Highway Fog Warning System: across the United States
• Idaho Storm Warning System: Idaho
• CARS: Iowa, Minnesota, Missouri, and Washington
• rWeather: across the United States
• OK-FIRST: Oklahoma
• ADVISE: Utah
• The Fog Warning System: California
• Automated Fog and Smoke Warning System: Georgia
• Weather Related Intelligent Speed Adaptation (WISA): Finland
• Weather Controlled Road and Investment Calculations: Finland
• Surface Transportation Weather Decision Support Requirements (STWDSR): across the United States

CASE STUDIES

Advanced Transportation Weather Information System (ATWIS) Research Program

System Description: The primary purpose of the ATWIS research program is to demonstrate how current technologies in weather forecasting, weather analysis, telecommunications, and road condition monitoring can be merged effectively to produce a safer and more efficient transportation system. The program demonstrates a prototypical advanced weather information system including a management center to support traffic weather analysis and forecasting in a responsive decision support environment.

The Advanced Transportation Weather Information project began in 1996 with the aim of providing route-specific short-range weather and road conditions to the traveling public and commercial vehicle operations. Cellular and wireless phone users can dial #7233 (#SAFE) along any Interstate, US, or state highway within North Dakota, South Dakota, and Minnesota.  After answering a few questions detailing their location and direction of travel, the caller is provided a road condition report and short-range weather forecast.

Results: The University of North Dakota conducted a study (1997-1998) to evaluate the use of ATWIS. The study showed that less than half the population surveyed was aware of the existence of #SAFE. Ten percent (10.5%) of all persons surveyed reported using the #SAFE. Following radio/TV advertising, highways signs were the most frequent way people reported becoming aware of #SAFE. Transportation Department maintenance crew supervisors were almost all daily users of weather information. Most used the forecasts for planning their activities, and they found the forecasts accurate. A majority (75%) said they had altered their assignment of personnel as a result of the daily forecast.

Source: ATWIS

National Differential GPS

The National Oceanic and Atmospheric Administration (NOAA) Forecast Systems Laboratory and Federal Highway Administration (FHWA) have initiated a joint project to investigate the use of National Differential Global Positioning System (NDGPS) sites for improved weather forecasting. The NDGPS is an augmentation to the Global Positioning System (GPS) and combines the navigational applications of GPS with meteorological remote sensing to measure atmospheric water vapor. As such, NDGPS is a useful tool for making accurate weather forecasts. It is also linked to cell phones to alert travelers and emergency personnel of adverse weather conditions.

System Description: NDGPS includes an NDGPS tower, water vapor sensors, and mobile receivers. The fixed location of an NDGPS tower is compared to the GPS-determined location of the tower. The measured difference between the actual location and the GPS location can be used as a correction factor. This factor or "signal" is transmitted to hand-held or in-vehicles mobile receivers. These receivers use the corrective signal to adjust the GPS location so that it becomes the more accurate NDGPS location. The closer the receiver is to the transmitter, the more accurate the correction and thus the adjusted location. NDGPS also measure the slowing of satellite signals by water vapor with great accuracy.

Source: National Differential GPS, Nationwide Differential GPS Water Vapor Observations During Hurricane Georgest & James, Arnold. New Applications make NDGPS more pervasive. Public Roads. January/February 2001.

FORETELL Field Operational Test

System Description: FORETELL collects, forecasts, and distributes highly specific road weather information that is pertinent to highway and trucking professionals, transit operators, everyday commuters, long-distance travelers, and all other road users. FORETELL is a multi-state initiative covering the Upper Mississippi Valley region funded in part by the Federal Highway Administration (FHWA). The mission of the FORETELL field operational test is to create a road weather information system (RWIS) fully integrated within a wider set of Intelligent Transportation System (ITS) services to enhance safety and facilitate travel throughout North America. Information provided by this system will be disseminated to the Iowa DOT and eventually be made available to other agencies and to the public via a variety of means such as: Highway Advisory Radio, Variable Message Signs and the Internet.

Source: FORETELL

Aurora

System Description: Aurora is a long-term program of collaborative research, development, and deployment of advanced technologies for detailed road and weather monitoring and forecasting. Aurora programs integrate road and weather technologies with weather monitoring infrastructures in order to forecast weather and provide real-time information to travelers. There are currently 5 completed Aurora projects and 16 on-going projects. One of Aurora’s completed projects is the Standardized Testing Methodologies for Pavement Sensors-Phase I. The purpose of this project was to establish and evaluate standard procedures for testing RWIS sensors, related software, and models. Phase I was aimed at identifying worldwide efforts to test and calibrate road weather sensors. This project determined that Aurora’s size and resources are not sufficient to fund an independent effort to develop test and calibration standards. A Phase 2 for this project has been funded and is aimed at finding ways to promote the development of national and international RWIS standards and procedures.

Source: Aurora Program

SAFE-PASSAGE Project

System Description: The project employs ITS technology to develop a predictive computer model to micro-forecast pavement temperatures and roadway conditions; provide real-time motorist information; and establish a rural traffic management center for reception, coordination, and dissemination of all relevant data. The SAFE-PASSAGE project is located on Interstate 90, a major east-west corridor between Chicago, Illinois and Seattle, Washington.

The system will also enable maintenance personnel to improve the timing of deicing chemical applications in this high elevation mountain pass corridor. The predictive model will be integrated with several traditional rural ITS technologies including Road and Weather Information Systems (RWIS), Variable Message Signs (VMS), Highway Advisory Radio (HAR), a Rural Traffic Management Center (RTMC), and Rural Advanced Traveler Information System (Rural ATIS).
Source: SAFE-PASSAGE

RWIS Programs

System Description: A Road Weather Information System (RWIS) uses historic and current climatological data to develop real-time road and weather information (i.e. forecasts) for roadway users. RWIS use specialized equipment and computer programs to monitor air and pavement temperatures in order to predict whether precipitation will freeze on the pavement. Sensors collect real-time data on air and pavement temperatures, precipitation, and the amount of deicing chemicals on the pavement. These are combined with information from value-added meteorological services to predict pavement temperatures for a specific area, such as a mountain pass, over a 24-hour period. These predictions are then transmitted to a computer at the highway agency's winter maintenance center. This information is critical to an effective anti-icing strategy, since deicing chemicals must be applied about an hour before the pavement reaches freezing temperatures. This prevents ice from forming on the pavement, in contrast to traditional methods in which the ice is cleared after it has already bonded to the pavement. Using portable computers linked by modem to the central computer, maintenance managers can monitor conditions and advise motorists and dispatch crews as necessary.

Source: RWIS

Tennessee Fog Detection and Warning System

In December 1990, a chain-reaction collision involving 99 vehicles prompted the design and implementation of a fog detection and warning system on Interstate 75 in southeastern Tennessee. The system covers 19 miles including a three-mile, fog-prone section above the Hiwassee River and eight-mile sections on each side.

System Description: Center managers with the Tennessee DOT and Tennessee Highway Patrol access a central computer system that collects data from eight fog detectors, and 44 vehicle speed detectors. By continually monitoring fog and speed sensor data, the computer system predicts and detects conditions conducive to fog formation, and alerts managers when established threshold criteria are met. Highway Patrol personnel visually verify onsite conditions.

The computer system provides decision support by correlating field sensor data with pre-determined response scenarios. Operational techniques include advising motorists of prevailing conditions via flashing beacons atop six static signs, two Highway Advisory Radio (HAR) transmitters, and ten Dynamic Message Signs, reducing speed limits using ten VSL signs (i.e., 50 mph or 35 mph), and restricting access to the affected highway section with ramp gates under the worst-case scenario (i.e., visibility less than 240 feet).

Results: There have been over 200 crashes, 130 injuries and 18 fatalities due to fog on this highway section since 1973. Since the installation of the fog detection and warning system in 1994, no fog-related accidents have occurred.

Source: Tennessee Fog Detection and Warning System

Maintenance Decision Support System (MDSS) Project

Project Description: The Maintenance Decision Support System (MDSS) project is a multi-year effort to prototype and field test advanced decision support components for winter road maintenance. The project’s prototype development phase is being conducted from September 2000 to September 2001, and an operational test phase will begin in October, 2001. The MDSS Prototype Development Project Plan describes the tasks, milestones, deliverables, and design elements for the development of the prototype.

System Description: This prototype will include mesoscale and ensemble forecasts, video cameras, and road weather sensors. These data will be sent to the National Center for Atmospheric Research’s dynamic, intelligent, forecast system (DICAST), which will generate point and time specific forecasts valid along road segments. The output will include probability information for each parameter. The diagnosed and forecasted weather data will be integrated with DOT operational data and passed to a road conditions module, which will generate information related to snow drifting, road temperature, and friction coefficient. These data will then be processed by a decision support system using rules of practice logic and presented to decision-makers on a geographic information system.

Source: MDSS, April 2001 & Mahoney, William. An Advanced Winter Road Maintenance Decision Support System. Eleventh Annual ITS American 2001 Meeting.

Mobile Road Condition Sensor Project

Project Description: The objective of the Mobile Road Condition Sensor project is to develop and field test a sensor system to be mounted on winter road maintenance vehicles that (1) detects and monitors thin films of ice, snow, water, and ice-water mixture on road surfaces and (2) provides real-time road condition information to the vehicle operator and to road maintenance and traffic management systems.

Potential applications include (1) Optimal application of surface treatments to reduce costs of winter maintenance operations and damage to the environment. (2) Provision of real time hazardous road condition information to traffic management systems, emergency response units and traveler information systems. 
Source: Mobile Road Condition Sensor Project & Maintenance Management: Mobile Road Condition Sensor Project

Fog Mitigation System in South Carolina

System Description: A fog mitigation system that monitors visibility conditions is in operation on I-526 near the Cooper River in Charleston, South Carolina. When weather conditions are hazardous, motorists are warned of adverse road weather conditions.

Source: US DOT ITS Fog Mitigation System

Highway Fog Warning System

The Highway Fog Warning System is the result of FHWA's study to develop a low-cost, reliable, fog sensor. The study was aimed at developing a cost-effective highway visibility sensor that measures the density of roadway fog and is linked to traveler information systems and could substantially reduce fog accidents.

System Description: Sensor units, containing nephelometers (devices that measure the light scattered in a forward direction by fog particles) were placed in several locations for this study. Spacing between sensor units was between 61 and 213 m (200 and 700 ft), covering the study area. With this configuration, patchy fog, as well as dense fog, could be monitored along the highway over a large area. The host computer requests fog density data from each sensor and determines the level of warning based on a pre-established conversion equation. The warning signal is then transferred to motorists through roadside displays or audio communication.

Results: Subsequent field tests have demonstrated the ability of the fog sensor to accurately determine fog density in a highway environment. Both laboratory and field tests have shown that this device can withstand the extreme temperature ranges, heavy rainfall, and blizzard conditions. Refinements based on field-testing experiences have been incorporated into the latest design of this device. Specific improvements in the production and testing of future sensors have been proposed.

Source: Highway Fog Warning System,Techbrief, April 1999

Idaho Storm Warning System

The Storm Warning Project was initiated in 1993 as a result of a large number of serious traffic crashes that occurred during periods of low visibility on I-84 in southeastern Idaho between 1988 and 1993. The purpose of the operational test was to investigate various sensor systems that could provide accurate and reliable visibility and weather data, and to use that data to provide general warnings, speed advisories, and possible road closure information to travelers on a section of I-84 in southeast Idaho that is highly prone to reduced visibility from blowing snow and dust. The primary goal of such a system is a major reduction in visibility-related multi-vehicle accidents in rural areas.

System Description: Sensors measuring traffic, visibility, roadway, and weather data were installed at the test site, and automatic traffic counters recorded the lane number, time, speed, and length of each vehicle passing the sensor site. To confirm visibility readings provided by the sensors, a video camera was installed at the test site and aimed at a series of target signs placed along the interstate at various known distances. During the course of the project, four variable message signs (VMS) were installed along the test section of roadway, to provide information to travelers regarding low visibility and other road condition information in the test area. Data generated by the sensor systems was transmitted to a master computer, which recorded readings every five minutes. This information provided a baseline of driver behavior, to help determine if the signs were causing drivers to change their behavior. Information was transmitted to the motorist via changeable message signs. Cost: Estimated Total ITS Funds: $804,500 Estimated Total Project Cost: $1,231,900.

Source: Idaho Storm Warning System Operational Test, Final Report, Idaho Transportation Department, December 2000.

Condition Acquisition and Reporting System (CARS)

System Description: The Condition Acquisition and Reporting System (CARS) is being developed for the states of Iowa, Minnesota, Missouri, and Washington to allow agencies at the local, state and national levels to report planned and unplanned road conditions, and weather traffic events. The system will permit State Police, Departments of Transportation, local and county governments and other public agencies to use a central collection system that will store road and weather conditions, as well as situations and courses of action. The system will be flexible enough to permit states to exchange information with adjoining states and information service providers, and disseminate information to the public via a web site. This system is currently under development.

Source: CARS (examples of CARS's statewide highway reports)

rWeather Web Site

The Washington State Department of Transportation (WSDOT) has undertaken development of rWeather, a real-time statewide system that collects and disseminates road and weather information. The web site provides access to real-time data from approximately 350 weather stations, traffic surveillance cameras, and mountain pass reports (during winter season) across the state. This application is currently being operated as a prototype.

Source: rWeather

Oklahoma's First-response Information Resource System using Telecommunications (OK-FIRST) Project

System Description: OK-FIRST is an initiative by the Oklahoma Climatological Survey to improve access to current weather information and to develop a decision-support system for the state's public safety (fire, police and emergency management) agencies.

OK-FIRST transmits current weather information to emergency managers in various public safety agencies. To aid in effective decision-making, the system provides tailored county-level, agency-specific weather information that allows emergency managers to accurately identify weather threats. OK-FIRST includes a web site and an electronic bulletin board system to foster communication and facilitate information sharing. Emergency managers have used OK-FIRST surveillance data to respond to severe weather (e.g., floods and fires) and HAZMAT incidents; to execute control (e.g., close bridges and interstate highways) in coordination with traffic managers; and to plan response (e.g., staff snow crews) in coordination with maintenance managers.

Source: OK-FIRST

The Fog Warning System in California

The Central Valley can experience extremely heavy fog during the winter months. Caltrans and the CHP began "Operation Fog" in 1991 in an effort to help make drivers aware of this hazard in the Central Valley and to reduce the number of fog-related accidents.

System Description: Caltrans established an automated "Fog" warning system in 1996 in San Joaquin County on southbound Interstate 5 and westbound SR 120, areas known for dense fog. The automated system consists of nine permanent Variable Message Signs (VMS), nine weather stations, and thirty-six speed monitor locations. The Fog Warning System automatically detects reduced visibility and speeds. The system automatically advises travelers, via the VMS, of speeds that would be safe for conditions ahead. When visibility is 0' to 100' the message "Dense Fog Ahead" will appear to alert the motorist of conditions ahead. When visibility drops to 201' to 500' – "Foggy conditions Ahead" would appear. When traffic speeds are 11 - 35 mph the message "Caution Slow Traffic Ahead" will be shown. When vehicle traffic speeds drop between 1 – 10 mph the message "Caution Stopped Traffic ahead" will appear on the VMS. In the event of an accident during foggy conditions the speed messages will override the fog messages.

Results: The Caltrans Fog Warning System has thus far been shown to deter vehicle accidents that usually result from thick fog or dust storms along I-5 and SR-120 in San Joaquin County.

Source: Caltrans Article

Automated Fog and Smoke Warning System in Georgia

A heavily traveled, 14-mile stretch of interstate highway in south Georgia cuts through a peat bog, which often produces extremely thick fog. Vehicle accidents and human fatalities have resulted due to the low visibility. Engineers at the Georgia Tech Research Institute (GTRI) in Atlanta proposed a solution, and in the summer of 2001, a $2.4 million, automated fog and smoke warning system will become operational on Interstate 75 near Adel, Ga., just 35 miles north of the Florida state line.

System Description: At the heart of the system's data collection operation is a set of 19 commercially available fog sensors. Each sensor has a transmitter and a receiver. The transmitter is angled away from the receiver, so that in clear conditions, its light beam misses the receiver. But when fog or smoke particles are present in the air, they scatter some of the light into the receiver. The sensor detects this light and sends a reading to the system's on-site computer. The computer, linked to the system's components via a fiber optic network, is located inside a building alongside the interstate in the fog zone. The computer collects data not only from the fog sensors, but also from an adjacent weather station, speed detectors on the highway and television cameras, which GDOT officials can operate remotely to scan the area. Also, the computer contains several telephone modem lines so officials can remotely upload and download data from the site.

The system's software analyzes data from the fog sensors, notifies GDOT officials at the Transportation Management Center (TMC) in Atlanta of potential problems and automatically decides what message to post on four changeable message signs on the north- and southbound outskirts of the fog zone. The 36-foot-wide and 9-foot-high signs are attached to metal structures built over the highway.

When the fog warning system detects a decline in visibility to a certain level, it automatically notifies the TMC and also sends a caution to motorists via the changeable message signs. It also turns on streetlights along the roadway. If visibility drops to a second threshold, the system again notifies the TMC and then issues a speed advisory to motorists via the signs. The system recognizes two additional lower levels of visibility and again alerts the TMC and issues advisories to motorists to further decrease their speed. TMC personnel plan to develop a protocol for notifying local officials, who could put GDOT people on the scene at some point as the visibility gets worse.

Results: The GTRI will conduct a follow-up on the warning system after it becomes operational. Researchers will pay special attention to the system’s maintenance requirements and accuracy as well as to human factors such as driver response to CMS.

Source: Georgia Tech Research News Article

Weather-related Intelligent Speed Adaptation (Finland)

System Description: The Technical Research Centre of Finland conducted a two-phased driving simulator study to compare adverse road condition driver support systems and to test a method of informing drivers of adverse road conditions. The study was performed using the advanced driving simulator of the Institute for Transport Studies at the University of Leeds, UK. This fixed-base simulator is a complete vehicle with all basic controls, operational dashboard instruments, and driver feedback provided via simulated steering forces in the steering wheel. The test route designed for the study consisted of a rural road with a 50 mph speed limit.

In phase one, 16 drivers drove the test route three times: unassisted in summer conditions, unassisted in winter conditions, and with a risk display in winter conditions. The risk display informed drivers about road surface friction with a warning bar that grew longer and changed color with increasing risk. In phase two, 24 drivers were used to compare the following driver support systems under winter conditions: no support system (i.e., typical winter driving feedback), an advanced driver information system, and the Weather-related Intelligent Speed Adaptation (WISA) system. The advanced driver information system included variable message signs indicating "ICE" if road surface friction was low. The WISA system prevented vehicles from exceeding a safe speed on icy road sections.

Results: In the first phase, average travel speeds in icy winter conditions were 2.5 mph lower than summer travel speeds, 39.0 mph (62.8 km/h). Although the risk display decreased speeds in sharp curves, test drivers suggested a more anticipatory system, which would warn drivers before they encountered a curve or icy area. In this phase, only one driver ran off the road on a sharp icy curve. In phase two, the coverage of low-friction areas was increased and the friction of non-icy sections was lowered to better correspond to normal winter conditions. Five drivers with no support system ran off icy road sections and five drivers ran off the road when using advanced driver information system. No test drivers assisted by the WISA system left the roadway.

Conclusions: It was concluded that driver adaptation to adverse conditions is not adequate because they cannot accurately assess the degree of road surface friction. The Weather-related Intelligent Speed Adaptation (WISA) system appeared to support drivers in adverse road conditions, increasing safety and travel speeds. More advanced measurement techniques are required to provide drivers with adequate road condition information and to recommend appropriate behavior modification.

Source: ITS Benefits Database (Measurement: Safety)

Weather Controlled Road and Investment Calculations (Finland)

System Description: The 8.7 mile test area is equipped with a road weather information system (RWIS) consisting of 36 variable speed limit signs, five variable message signs (VMS) displaying graphical and textual information, and two environmental sensor stations (ESS). Each ESS measures wind speed and direction, air temperature, pavement and sub-surface temperature, humidity, precipitation rate and accumulation, and pavement condition. The western ESS nearest the sea also measures precipitation type and visibility. Variable signs are automatically controlled by the RWIS or manually controlled by operations personnel. Manual control is used if the variable signs automatically display information that does not correspond to actual conditions. Variable speed limit signs are divided into 12 separately controlled groups, with signs in a single group displaying the same speed limit.

Results: The divided roadway section typically has speed limits of 75 mph in the summer. In the winter, recommended speed limits vary between 50 mph and 62 mph based on road and weather condition data collected from the ESS. Recommended speed limits are based on pavement condition, precipitation, visibility and wind. Heavy precipitation, wet pavement conditions, reduced visibility, and wind speed all reduce the speed limit. When speed limits are reduced, VMS display the reason for the reduced speeds. Three symbols indicating "slippery road surface," "hazardous conditions ahead," or "road construction ahead" may also be displayed on VMS. If speed limits are not reduced, VMS display only air and pavement temperatures.

Conclusions: It was estimated that the average speed decreased 0.4 to 1.4 percent due to the RWIS. The average yearly accident rate was projected to decrease by eight to 25 percent. This impact on safety is due to lower average speeds when accident risk is greatest (i.e., when poor road conditions exist).

Source: ITS Benefits Databse (Measurement: Safety)

Web-based Traffic Information and Weather Events in the Seattle Puget Sound Region

System Description: The Seattle Metropolitan Model Deployment Initiative (MMDI) measured driver use of Advanced Traveler Information System (ATIS) weather sites on a highly utilized multi-modal transportation system. The evaluation area was a 300-square-kilometer (116-square-mile), mixed freeway/arterial network north of downtown Seattle.

As part of the initial MMDI evaluation, Washington State's Department of Transportation (WSDOT's) traffic web site utilization was tracked using WebTrends™ log analysis software. A section of web site usage was examined for three months: May 1998, December 1998 and April 1999. A weather event was defined as the combination of AM and PM peak periods where the measurable water equivalent rainfall was 0.01 inches (0.25 mm) or greater. Using this criteria, 16 of 64 days were deemed weather event days and one of the 64 days was deemed a snow day.

Results: Analysis of the weather and web site usage data revealed that (1) during a weather event, web site activity – measured in average page views – increased by 26.52 percent, (2) that there was a 69.09 percent increase in average page views during a snow event and (3) that ATIS penetration is not evenly distributed as originally assumed (i.e., when there was some type of weather event, web site activity increased). These results were used to develop a non-uniform distribution of ATIS users, while maintaining an average of six percent. Non-uniform values were found to be 5.70 percent during non-weather events, 7.22 percent during weather events and 9.66 percent during snow events. The results of the network analysis show that a non-uniform ATIS utilization rate related to severe weather has a small positive impact on roadway system efficiency.

Source: ITS Benefits Databse (Measurement: Safety)

Surface Transportation Weather Decision Support Requirements (STWDSR) Project

Project Description: In 1999, the FHWA's Road Weather Management Program launched the Surface Transportation Weather Decision Support Requirements (STW) project to (1) define weather information needs of surface transportation users and (2) ultimately aid in improved decision-making to reduce the negative impacts of weather on roadway networks. The primary objectives of the STWDSR project are to provide high-level requirements for a Weather Information for Surface Transportation Decision Support System (WIST-DSS) and to identify external information requirements. The first version of the Surface Transportation Weather Decision Support Requirements (STWDSR V1.0), completed in January 2000, includes a thorough account of the weather information needs of all users and operators. STWDSR V2.0 was completed in July 2000 and describes the operational concept for the Weather Information for Surface Transportation Decision Support System (WIST-DSS).  STWDSR V3.0 and V4.0 will expand the scope of user requirements to include decisions of emergency managers/traffic managers (EM/TM) and highway users or travelers. The process to develop STWDSR V3.0 and V4.0 is well underway, with the latter estimated to be completed by October 2001. The STWDSR documents will guide FHWA's program of research and development, operational tests, and deployment guidance.

REFERENCES

Hallowell, Robert. Utilizing FAA-Developed Automated Weather Algorithms for Improving Surface Transportation Operations in Adverse Weather. Eleventh Annual ITS American 2001 Meeting, June 2001.

Hansen, Blake. Road weather information systems: some findings on how RWIS information should be disseminated to the traveling public. Transportation Research Board. Meeting (80^th: 20), p. 21, 2001. PATH record no. 22294.

Hansen, John. What does weather have to do with it? Institute of Transportation Engineers, p.4, 1999. PATH record no. 17198.

Happy Motoring on Safer Interstate Highway, Georgia Tech Research Horizons, July 2001.

Idaho Storm Warning Project Operational Test, Final Report, University of Idaho/Boise State University, December 2000 Link to Report

Sas, Mary. Weather prophecy: roadside detectors take control. Traffic technology international, pp. 43-44, 1999. PATH record no. 15971.

Stowe, Robert. A benefit/cost analysis of intelligent transportation system applications for winter maintenance. Transportation Research Board Meeting (80^th: 20), p. 13, 2001. PATH record no. 21973.

Links

Road weather information systems research
http://www.aurora-program.org/

Author: Lauren Smith, last update: 11/01/01