About RWIS

What is a Road Weather Information System?

The Alaska Department of Transportation and Public Facilities (ADOT&PF) operates a network of road weather stations strategically located along the highway system - the Road Weather Information System (RWIS). The RWIS site is composed of four components: collection (Environmental Sensor Station - ESS), processing (remote processing unit - RPU), disseminating, and transmitting. The ESS is composed of an array of three categories of environmental sensors: atmospheric, surface/sub-surface, and water/snow level. The RPU collects and processes ESS sensor measurements. The RPU also provides the ESS observation to that communications device (phone lines, wireless radios, communication network, internet) that transmits the data to a central server using a communication protocol standard. Agency personnel access the real-time pavement and weather data via computer workstations at the maintenance office.

Alaska's RWIS stations may include some or all the following:

• pavement sensors in travel lanes to measure surface and subsurface (17" below the surface) temperatures
• atmospheric sensors adjacent to the roadway to measure: air temperature, dew point temperature, relative humidity, wind speed and direction, precipitation occurrence, precipitation accumulation, atmospheric station pressure, snow depth, or stream water level
• closed circuit cameras that take images of the roadway for snow and ice control as well as for traveler information. ADOT&PF also provides images of mountains and passes to supplement the Federal Aviation Administration web camera program

Why collect RWIS data?

Real-time information enhances the ADOT&PF's ability to conduct road maintenance operations in a safe and efficient manner. This and other weather information allow the ADOT&PF to schedule maintenance personnel and equipment based on current and forecast weather and pavement surface conditions. Real-time weather information:

• improves timeliness of maintenance actions
• increases winter maintenance efficiency
• minimizes the traveling public's exposure to hazardous weather related roadway conditions.

Road Weather Information System site at Bird Point on the Seward Highway

Does the ADOT&PF share RWIS data?

Yes. The ADOT&PF openly shares RWIS data with the National Weather Service, the Federal Aviation Administration, the University of Alaska, and Elmendorf Air Force Base. For a complete list of partners, see Partnerships.

How Are RWIS Locations Selected?

The primary consideration for new RWIS sites is the Department's Maintenance & Operations (M&O) personnel in making winter maintenance decisions such as snow plowing and anticing/deicing applications. Other considerations include the National Weather Service using the observations to improve local forecasting and weather warnings the and the public for making informed travel decisions. Other agencies also benefit from RWIS sites, such as the Federal Aviation Administration's Web Camera program.

Once we selected a new site, we determine if the site is a good fit for our over RWIS deployment plan. Other significant factors are cost and whether power and communication are available. Sites that don't have direct power require a power generator, while sites that do not have nearby telephone or State of Alaska network service require a wireless communication solution. Other factors include topography, the natural environment around the site that can affect sensor readings, and the availability of State right-of-way.

However, with increasing emphasis on Homeland Security nationally, federal and state law enforcement agencies have encouraged us to archive images for criminal law enforcement. Thus, while no traffic enforcement activity is contemplated with the RWIS system camera images, these images may be retained and used for criminal law enforcement, including Homeland Security, should the need arise.