Collaboration Across the Road Weather Enterprise: The Pathfinder Project

CHAPTER 2. APPLYING ROAD WEATHER FORECASTING IN YOUR STATE

Figure 2. Photo. Road Weather Information Helps Maintenance Activities Run Smoothly.
(Source: Wyoming Department of Transportation)

The Benefits of Road Weather Forecasting in a Nutshell

Access to high-quality road weather information helps decision makers improve safety, enhance traffic flow and travel reliability, and increase agency productivity. Road weather mitigation strategies enhance roadway safety by: Reducing crash frequency and severity. Restricting access to hazardous roads. Encouraging safer driver behavior. Road weather management strategies enhance traffic flow and mobility by: Allowing the public to make more informed travel decisions. Promoting more uniform traffic flow. Reducing traffic congestion and delay, and minimizing the time to clear roads of snow and ice. Productivity is increased through better interagency communication and data sharing, and by reduced labor, material, and equipment costs for snow and ice control operations.

USE OF ROAD WEATHER INFORMATION IN MAINTENANCE OPERATIONS

Maintenance managers obtain and make extensive use of road weather information such as pavement temperature forecasts, water, snow and ice accumulation, and road condition predictions. This information helps managers make proactive decisions for a variety of winter and non-winter maintenance activities, including decisions about staffing levels, the selection and timing of maintenance activities, and resource management (such as personnel, equipment, and materials) as well as road treatment strategies during winter storms.

Winter road maintenance activities are especially sensitive to weather conditions. Some of the most common weather conditions experienced throughout this season of the year include snow, ice, frost, freezing rain, and fog. Other conditions, such as blowing snow further complicate these weather aspects. During this period of the year, maintenance tasks can often involve snow and ice treatment strategies, including plowing snow, spreading abrasives to improve vehicle traction, and dispensing anti-icing/deicing chemicals to lower the freezing point of precipitation on the pavement. In regions with heavy snowfall, maintenance managers may erect snow fences adjacent to roads to reduce blowing and drifting snow. Other mitigation strategies may include the use of slope sensors and avalanche forecasts to minimize landslide and avalanche risks. When a slope becomes unstable because of snow accumulation or soil saturation, roads in the slide path may be closed to allow the controlled release of an avalanche or landslide. After snow, mud and debris are cleared and damaged infrastructure repaired, the affected route can be reopened to traffic.

Figure 3. Photo. Fog is a Common Weather Condition Affecting Visibility.
(Source: Georgia Department of Transportation)

Many non-winter maintenance activities are also affected by weather conditions. Mowing is conducted on a cycle throughout the summer months but will be suspended during heavy rain and thunderstorms. The spraying of herbicides is not conducted during rainstorms or high winds. Striping requires a dry roadway, no high winds, a minimum ambient air temperature, and no immediate likelihood of rain. Surface repairs (such as pothole and seam repairs) using hot mix asphalt need dry pavement with a minimum ambient air temperature and no risk of rain in the short term. Many maintenance activities will also be suspended for thunderstorms, tornado forecasts, and periods of low visibility to protect the safety of both maintenance personnel and travelers who may unexpectedly encounter maintenance equipment on or near the roadway.

Examples of Additional Collaboration Events
Red Flag (Fire Weather) Warnings Burn Bans. High Winds. Flash Flooding.

USE OF ROAD WEATHER INFORMATION IN TRAFFIC OPERATIONS

The FHWA RWMP is working with State and local transportation agencies to become more proactive in the way they manage traffic operations during weather events. Weather-Responsive Traffic Management (WRTM) is the central component of the program's efforts. WRTM involves the implementation of traffic advisory and control strategies in direct response to or in anticipation of developing roadway and visibility issues that result from deteriorating or forecasted weather conditions.

Over the past 10 years, transportation agencies have implemented a variety of strategies to mitigate the impacts of adverse weather on their operations. These strategies range from simple flashing signs to coordinated traffic-control strategies and the dissemination of regional TI. Operational strategies that traffic managers are currently using include:

• Motorist advisories, alerts, and warnings intended to increase the awareness of the traveler to current and impending weather and pavement conditions. Approaches include active warning systems that warn drivers of unsafe travel conditions through a particular section of roadway, often in remote or isolated locations; pre-trip road condition information and forecast systems; and en-route weather alerts and pavement condition information.
• Speed-management strategies designed to manage drivers' speed during inclement weather events. This includes both advisory, which usually involves posting an advisory travel speed deemed safe by the operating agency for the current travel conditions, and regulatory, which include speed limits that change based on road, traffic, or weather conditions.
• Vehicle restriction strategies involve placing restrictions on the types or characteristics of vehicles allowed to use a facility during inclement weather events. These strategies might include size, height, weight, or profile restrictions.
• Road restriction strategies restrict the use of a facility during inclement weather to help travelers avoid sections of roadway that are dangerous.
• Traffic signal control strategies involve making modifications or influencing the way traffic signals operate during inclement weather to allow for more uniform traffic flow based on the prevailing or predicted weather conditions.

USE OF ROAD WEATHER INFORMATION BY MOTORISTS AND COMMERCIAL VEHICLE OPERATORS

Traffic managers disseminate road weather information to road users of all types to influence their travel decisions.

Motorists make travel decisions by using traveler information (TI) via roadway infrastructure, telephone systems, websites, broadcast media, and interactive smart phone applications that have road weather information both pre-trip and en-route.

Road weather TI applications are being tailored to different road users allowing them to make informed travel decisions regarding travel mode, departure time, route selection, vehicle type and equipment, speed choice/selection, and driving behavior. In the event of a road closure, travelers will need alternate route information.

Commercial vehicle operators will also use this information as well as information from their truck dispatchers for travel decisions. Commercial vehicle operators are especially sensitive to time delays and may need additional information about road restrictions caused by high winds, height and weight limits, or subsurface freeze/thaw conditions. These applications use detailed information and allow for the dissemination of road weather information in a standard, easy to understand format.

While different types of road users have varying information needs, it is important to have consistent information when disseminated from different sources.

Did You Know?
Pathfinder identified additional areas for future expansion of road weather information including further integration with the Commercial Trucking Industry and Emergency Services. Visit http://ntl.bts.gov for more information.

Key Points

Road weather and weather are closely related, however it is important to stress that weather forecasts are not intended for giving motorists detailed information on the road weather conditions. Road weather and weather forecasts need to be differentiated from one another, as well as standardized so that road users and managers can make appropriate decisions regarding travel. Road weather and weather forecasts must address both current and predicted conditions.