Publication Number: FHWA-SA-98-021
Date: April 1998

Pennsylvania DOT Finds RWIS Station a Wise Investment

Investing in new technology always raises a question: Will the benefits of the technology justify its costs? To find out the answer for road weather information systems (RWIS), the Pennsylvania Department of Transportation (DOT) tracked the installation costs and the resultant savings in labor, materials, and equipment for one RWIS station along a section of Interstate highway. The highway agency learned that over two winters, the RWIS station saved the State more than $57,000.

The RWIS equipment was installed in 1989 on Interstate 80 in Venango County in northwestern Pennsylvania. The total installation cost was $118,434, including labor, materials, equipment, and telephone and electrical lines. Approximately $30,000 of the total was for a personal computer and other equipment needed to receive and review RWIS data at the district maintenance office. This equipment can handle signals from several RWIS stations, so the district would not need to purchase additional equipment when more RWIS stations were added.

The costs to operate the RWIS station were also taken into consideration. Electrical and long-distance telephone service cost $2,540 in 1990-91 and $2,803 in 1991-92. And in late 1991, one of the sensors failed and was replaced by a DOT crew at a cost of $1,948.

To calculate the savings resulting from installation of the RWIS station, Pennsylvania DOT first looked at the cost of winter maintenance on I-80 in Venango County. The county typically uses two trucks to keep I-80 clear of ice and packed snow. During the first winter studied, the cost to operate these trucks and spread salt and sand was $154 per hour; the cost increased to $174 per hour the following winter.

Pennsylvania DOT next looked at the winter storms that struck Venango County to determine the role the RWIS data played in the agency's response. When the RWIS data indicated that the pavement temperature was above freezing, Pennsylvania DOT delayed or canceled the deployment of trucks or brought them off duty early. In other cases, RWIS data showed that there was enough salt or other chemical on the road to prevent ice from building up and that additional applications were not needed. In some cases, RWIS data permitted the county to effectively use an anti-icing strategy, in which salt and other chemicals are applied to the road before a storm hits, to prevent the buildup of ice and packed snow. Because anti-icing strategies are more efficient, they typically require less salt or other chemicals than conventional deicing strategies. In all of these situations, the RWIS data helped reduce the cost of winter maintenance operations.

After subtracting operating costs, Pennsylvania DOT estimates that the RWIS station saved the State $20,715 in the first winter studied and $37,132 in the second winter. That's about a 50 percent return on investment in just 2 years.

Pennsylvania DOT says the total savings are actually much higher. The RWIS station provides data that are also used to schedule winter maintenance for much of southern Venango County, not just I-80. And because the anti-icing strategy calls for less salt and sand, there will be lower cleanup costs and less damage to bridges, pavements, and equipment.

RWIS has become a valuable tool for winter maintenance in the county. "We didn't realize how much we relied on the sensors until the week the system was down" in January 1992, said William McQuiston, Pennsylvania DOT's assistant county maintenance manager for Venango County.

State and local agencies also make use of the RWIS data. For example, local school districts call the district maintenance office's radar room, which monitors RWIS data and other sources of information on weather conditions, when bad weather threatens. "We're their main source of detailed information for use in deciding to delay or close schools," says Doug Scofield of the Pennsylvania DOT district office in Venango County.

Tracking the benefits and costs of the RWIS installation in Venango County helped Pennsylvania DOT commit to using RWIS technology. The State now has 27 stations, and "we plan to add considerably more in the next 2 years," says Tucker Ferguson, who manages implementation of new technology for Pennsylvania DOT. In March, the highway agency issued a request for proposals to install 20 more sites.

For more information on the Pennsylvania DOT study, contact Tucker Ferguson (phone: 717-787-6263; fax: 717-705-1426; email: tuckerferg@aol.com).

For more information on RWIS technology, contact Salim Nassif at FHWA (phone: 202-366-1557; fax: 202-366-9981; email: salim.nassif@fhwa.dot.gov).

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