ODOT deploys massive wireless Environmental Sensing Station technology in RWIS expansion

Keith C. Swearingen, P.E., P.S.
Administrator, Office of Maintenance Administration
Ohio Department of Transportation
Columbus, Ohio

The Ohio Department of Transportation (ODOT), already active in Road Weather Information Systems (RWIS) with 72 sites in the Columbus, Cleveland and Toledo areas, has recently expanded the system statewide with 88 NTCIP-compliant, uniquely-designed wireless Environmental Sensing Stations (ESS) and more than 160 additional pavement sensors on Ohio's roads.

The expansion brings the total number of reporting stations to 160, with over 400 pavement sensors statewide. This will  provide ODOT, city and county highway managers and the general public with a real-time weather and pavement condition resource.

Several factors make this deployment unique besides its sheer numbers and aggressive installation schedule which was four months, over the winter. The new ESS sites were designed to be completely wireless, combining wireless pavement sensors with solar power and a mixture of Radio Frequency (RF) to ethernet and IP over cellular communications. "We had a need to collect information from interstate and other primary routes in the rural parts of the state, not just in cities," said Abner Johnson, ODOT RWIS Coordinator. "Before, we could not collect enough data in rural areas to be helpful without it also being expensive."

Now ODOT's ESS sites using radio frequencies report at one minute intervals 24/7 with no recurring monthly fee. ESS sites using IP over cellular report every five minutes 24/7 for approximately $60 per month, per site. The same reporting cycle using conventional phone line would cost thousands per month. Both communication methods employ newer "push" technology from the remote site rather than "pulling" by server polling.

But probably the most exciting design feature is the use of multi-vendor technology. ODOT's ESS sites are equipped with NuMetrics Pavement Sensors, Vaisala Atmospherics Sensors, and Surface Systems ScanCast capabilities. This is the first time competing vendors have deployed integrated equipment on this scale.

"RWIS is a great decision support tool which ODOT and local agency responders can use to determine the beginning and ending of winter weather events and for planning other maintenance activities," Johnson said. "RWIS reports information directly from the highway, where the wind speed or temperature may be different from temperatures at airports or other local reporting stations, such as schools. As spring approaches, we all have maintenance responsibilities that pop up. The sensors give real-time, accurate data on the wind speed or pavement temperature of a specific area which is beneficial for activities such as crack sealing, or to let maintenance coordinators know if activities such as line striping or pesticide spraying will be feasible for the day, allowing maintenance personnel to plan a response that is not only effective, but efficient as well."

Summit County's Road Maintenance Manager, Gary Ellison, says RWIS has been an extremely helpful tool. "We use RWIS quite regularly to predict when storms will hit and either get out there early to pre-salt or know that we can hold crews off because pavement temperatures aren't cold enough for things to freeze."

A typical RWIS station with integrated Vaisala Atmospherics devices with wireless NuMetrics pavement sensors. By utilizing solar panels and cellular communications, ODOT has the flexibility of installing these devices anywhere along the highway.
Ellison said the more Summit County learns about RWIS, the more useful it becomes. "It keeps a history of events so we can track different storms, salt use, manpower and then look back on what we did to plan for the future."

Ellison said Summit County also uses RWIS to track storms across the county. "The storm may start in one part of the county while in the other half, our guys are still patching potholes. Using RWIS, we can track it as it's moving, see the type of precipitation, what it's doing to the roadway and how our crews in that area are combating it."

The pavement sensors also monitor traffic speed, traffic volumes and wind speed, making the system useful year-round. An added feature of these pavement sensors is the ability to report vehicle speeds, volume and classifications at specific locations. "Some state and federal funding is based on traffic volume," Johnson said. "RWIS is a great way for local governments to get the latest information on the number and type of vehicles traveling through the area."

For more information on RWIS, contact Keith Swearingen at (614) 466-3264 or Abner Johnson at (614) 466-4859.