This project used surveys to evaluate the impacts of improved Road Weather Information Systems and Highway Advisory Radio on the behavior, safety, and efficiency of commercial vehicle operators (CVOs), regional traveler information seekers, and WSDOT personnel responsible for maintaining operations along the US-395 corridor, north of Spokane, Washington.
Prior to the project, closed circuit television (CCTV) camera coverage and on-site Highway Advisory Radio (HAR) systems were not available. Internet traveler information only covered conditions in the immediate Spokane area and traffic reports were only available periodically on radio stations. In 2002, the project integrated two Environmental Sensing Stations (ESS) with a regional Road Weather Information System (RWIS) and Transportation Management Center (TMC), and deployed two mobile HAR systems to broadcast traveler information in the immediate areas of Loon Lake and Laurier area on US-395, and at Sherman Pass on SR-20.
The two new ESS installations were equipped with pole mounted CCTV cameras and sensors to measure pavement temperature, surface condition, solution freeze point, sub-grade temperature, wind speed/direction, precipitation type/intensity, visibility, air temperature, relative humidity, and atmospheric pressure. The data collected at each site were transmitted to WSDOT operators and relayed to the TMC in Wenatchee where pass condition information was posted on the WSDOT website and made available at a toll-free telephone number. HAR trailers were programmed to broadcast road and weather restrictions information using limited range radio transmitters.
The evaluation project was designed to measure changes in users’ decisions before and after deployment with consideration given to maintenance procedures, trip timing, trip routing, and level of preparedness. Baseline data (before equipment installation) were collected during the winter of 2000-2001, and post-deployment data were collected in the winter of 2002-2003. The evaluation team estimated that the duration of the post-deployment period (December 2002 through March 2003) would be sufficient time to allow travelers and operators to become aware of system components and use the information provided.
WSDOT Operations and Maintenance Personnel
Interviews were performed before and after the project implementation. "Before" data included a series of interviews with the WSDOT Eastern Division Traffic Engineer and members of the Operations field staff in Spokane and Colville. The interviews were designed to determine the operational and maintenance procedures in operation prior to deployment. "After" data included TMC event logs, event records, personal visits, and phone discussions with key personnel involved in WSDOT O&M activities.
Based on the data collected, evaluators generated a 3 month post deployment profile of O&M activities, and compared the "before" and "after" data to gain an understanding of the magnitude of system impacts.
The bullets below highlight major findings. The author noted the results may exhibit a high degree of uncertainty since the baseline data represented a limited number of storm events (2 storm events) compared to the post deployment data (15 storm events).
- The WSDOT used the RWIS-ESS data and National Weather Service forecasts to determine when and how much liquid anti-icing chemicals to deploy prior to a storm arrival.
- The maintenance superintendent reported that the RWIS-ESS data and camera images helped staff become more productive by allowing them to check road conditions in outlying areas and minimize unnecessary trips.
- The WSDOT road maintenance crews ranked RWIS pavement conditions data as the most useful ITS technology deployed, followed by camera images, and radar data on the Internet.
The author noted that WSDOT introduced anti-icing chemical operations during the post-deployment period, an important variable to consider when comparing the "before" and "after" data.
Commercial Vehicle Operations
In the spring of 2001, the WSDOT and Washington Trucking Association conducted baseline telephone interviews with 42 commercial vehicles operators estimated to be representative of the community of commercial trucking companies in the region. Thirty-five of 42 companies interviewed during the baseline period were available for follow-up telephone interviews; therefore, four additional trucking companies were interviewed during the post-deployment period.
The baseline and post-deployment telephone interviews were conducted using similar methodologies; however, the post-deployment interview guide was updated to account for the new ITS services installed after the baseline. The author noted that the size of the CVO companies interviewed had an operational capacity of 1-26 trucks, with a median number of 3 trucks per company. This indicated the sample set surveyed included many smaller companies and only a few large companies.
During the post deployment period, 39 CVOs were surveyed and asked, "Has the availability of HARs, camera images of key roadway segments, and enhanced Internet information affected driving safety for you in this region compared with last year?" Eleven of the respondents said they did not know whether their drivers used these information sources, or they themselves did not use them. Of the remaining 28 CVOs, 16 (57 percent) said the availability of the new information made them "somewhat" or "a lot" safer. The remainder (12 CVOs, 43 percent) said the safety benefit to them was "about the same as before." No one reported a reduction in safety benefit.
Twenty-two (56 percent) of those interviewed during the post-deployment period indicated they tuned-in to one or both of the HAR stations while traveling in the area. 20 (51 percent) found the HAR messages useful, assisting in their travel. Five (13 percent) found them "very useful," and 15 (38 percent) found them "somewhat useful." Overall, about one-third of CVOs interviewed indicated they would change routes based on road weather condition information provided, however, few were able to identify viable alternate routes in the study area.