Rural Research Matters InnovatIon - IntegratIon - ImplementatIon

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OverviewHighway systems are designed and operated for assumed “normal” conditions. In other words, designs focus on clear, dry pavement conditions, with limited consideration given to weather. When weather is taken into consider-ation, it is typically done so for an assumed light rain/wet pavement scenario. This fails to take into account condi-tions that have a significant impact on highway safety and operations, including snowfall, heavy rain, fog, and oth-ers. Such weather affects visibility and traction/friction, with direct impacts to critical design factors such as sight distance and stopping sight distance.

The impacts of weather are significant. According to the Federal Highway Administration’s “Road Weather Man-agement Overview”, weather impacts are the second largest cause of non-recurring congestion, with snow, ice and fog causing 15% of non-recurring congestion. Even low-impact events, such as light rains, can increase travel time delays by 12% to 20%. The economic impacts of weather-related delays are also significant; figures show that such costs to the trucking industry in metropolitan areas alone approach $3.4 billion, including approximately 32 million wasted hours.

In light of these facts, there is a need for both the highway system and motorists to address and adjust to inclem-ent weather. In doing so, safety and efficiency improvements may be achieved despite impacting weather events. Present designs and behaviors that specifically should take into account inclement weather include:– Drivers – increased level of attentiveness – Speed selection– Gap acceptance behavior– Lane changing– Etc. – System: design inputs are different during inclement weather – Minimum safe stopping distance – Traffic signal parameters– Minimum curve radii – Etc.

Systemwide ApplicationsMaintenance Management Vehicle Systems – Detroit/Oakland County, MI (1)

• Incorporated environmental and vehicle system sensors • Environmental sensors employed – Air temperature – Pavement temperature • System allowed real-time assessment of changing weather conditions • Resulted in improved roadway maintenance, safety and mobility – Iowa Concept Maintenance Vehicle (2 )

• Incorporated environmental sensors – Air temperature – Pavement temperature • System allowed real-time assessment of changing weather conditions • Pavement and air temperature sensors performed reliably • Problems encountered with other vehicle sensors prevented meaningful use of the data and conclusionsAnti-icing/Deicing – Idaho (1)

• Managers monitored data from web-based weather forecasts • Vehicles deployed in advance of threatening weather • Mobility, productivity and safety enhancements achieved through this approach – Virginia (3)

• Employed a fixed automatic spray technology (FAST) system • Atmospheric and road surface sensors employed to monitor current site conditions • Fixed anti-icing system activated if freezing expected • System did not accurately measure conditions present at the site and activate the Maintenance Decision Support System (MDSS) – 2007 - 21 state agencies using or developing MDSS tools – Pooled Fund Study (4)

• 14-state effort • Employs weather data from in-situ and remote sensing technologies, RWIS and weather forecasts • Provides road condition forecasts and real-time treatment recommendations • Presently in demonstration • Anticipated maintenance, safety and mobility improvementsRoad Weather Information for Travelers – Nebraska (1)

• Data collected from environmental sensor stations, Agricultural Weather Network, National Weather Service and Federal Aviation Administration • Weather forecast processing performed for 6.2 mile grids statewide • Tailored road weather information disseminated via 511 and the internet • Provided for more informed travel decisions and improved Department of Roads labor productivity – Washington (1)

• 50 environmental sensor stations – Collected air temperature, atmospheric pressure, humidity, wind speed and direction, visibility, precipitation, pavement temperature and subsurface temperature • Data fusion and modeling performed to determine prevailing and predicted conditions • Weather information disseminated via internet and telephone • Better informed travelers and improved safetyHurricane Evacuation Operations – South Carolina (1)

• Traffic flow monitored at 2 permanent vehicle detection sites and additional portable detection sites – Portable DMS and HAR sites used during reentry operations to alert/inform drivers • Systems facilitated contraflow operations – Allowed increased capacity and improved mobility during reentry operations

Site-Specific ApplicationsEnvironmental Monitoring System – Houston, Texas (1)

• 164 sensor stations – Collectively measured rainfall rate, accumulation and water levels, wind speed and direction, pavement and air temperatures, and ice and/or roadway water depth • Eliminate site trips to check conditions, improved safety and mobility by providing additional traveler information – Oklahoma (1)

• 110 sensor stations • Obtain county-level weather data (sensor systems employed unspecified) • Improved warning of hazardous weather and subsequently, public safetyWeather-Related Incident Detection – Virginia (1) • 120 monitor 56 miles of roadway – Consists of inductive loop detectors and CCTV cameras • Incident detection software analyzes field data to identify traffic disruptions – Included algorithms for clear, rainy and snowy conditions, specified by managers through CCTV observations • Weather incident detection enhanced mobility and safety through timelier response and clearanceFlood Warning System – Dallas, Texas (1)

• Automated system monitored water levels at 40 sites – System consisted of stilling wells, processing units and DMS • Warned drivers of high water until road barricaded • Improved driver safety and eliminated flooded road related damage claims – Palo Alto, California (1)

• Installed at 5 sites – Web-based system used water level sensors, rain gauges, flood basin detectors, tide monitors and CCTV • Automated telephone warnings for residents in threatened areas, web-based information for travelers • Improved driver safety through timely traveler information, increased staff productivity through elimination of on-site checksSpeed Management Systems – Washington (1)

• Variable Speed Limit (VSL) system – Employed 6 environmental sensor systems, 22 radar vehicle detectors, 13 DMS’ and an unspecified number of variable speed limit signs – Environmental sensors detect air temperature, humidity, precipitation, wind speed, pavement temperature and condition, and chemical concentrations at each site • Data processed by central computer to calculate safe speeds and suggest speed limit reductions to operators – DMS and VSL’s activated by operators as warranted • Improved safety through speed management – New Jersey (1)

• Advanced Traffic Management System – 30 environmental sensor stations collect wind speed and direction, precipitation type and rate, barometric pressure, air temperature, humidity, and visibility – Additional data collected via inductive loop detectors and CCTV • Personnel monitor environmental data to determine when speed limits should be lowered • Speed changes conveyed via 120 variable speed limit signs, DMS and HAR • Safety improved through effective decreases in traffic speedsWeather-Related Signal Timing – Charlotte, North Carolina (1)

• Weather-related signal timing plans used at 149 signals – CCTV cameras used to assess traffic and weather conditions • During rain, snow or ice conditions, operators manually implement weather-related timing plans – Plans downloaded to field controllers from central computer • Traffic speeds decrease when plans are implemented, but safety improves – Clearwater, Florida (1)

• Computerized traffic control system – System handles 14 signals • Predetermined preemption command sent to signals when specific rainfall amount occurs – Rain gauge mounted to one signal is connected to signal controller – Information sent back to central processing location • Congestion prevented and mobility enhancedAnti-Icing/Deicing System – New York City (1)

• Fixed anti-icing system on a portion of the Brooklyn Bridge

• Operators consult CCTV and weather forecasts to make treatment decisions • When conditions warrant, the fixed system is activated • Section of bridge with the system had a higher level of service, while safety and mobility were improvedAvalanche Warning System – Wyoming (1)

• System consists of sensor assembly, controller and two static warning signs with flashing beacons – Controller monitors sensor status and activates warning system when avalanche detected • Improved safety for drivers and maintenance personnel, and allowed timelier inspections to occurLow Visibility Warning System – Tennessee (1)

• System covers 19 miles of roadway – Consists of 2 environmental sensor stations, 8 visibility sensors and 44 vehicle detectors • On-site computer predicts and detects fog conditions – Alarm sent to highway patrol when fog conditions detected • Reduced speed message posted to DMS and troopers sent to patrol – Highway closed in worst-case conditions • Safety greatly improved following deployment – California (1)

• System employs 36 vehicle detection site and 9 environmental sensor stations – System included a rain gauge, and sensors measuring visibility, wind speed and direction, humidity, barometric pressure, and air temperature • Software processes vehicle speed, visibility distance and wind speed, displaying warning messages on DMS’ when warranted • Improved safety in low visibility conditionsWind Warning System – Montana (1)

• Warns high-profile vehicles of high winds on 27 mile roadway segment • Environmental sensing station tracks wind speed and direction • Managers alerted when severe crosswinds are detected – Post warning messages to DMS’ in the area • Safety improved as did maintenance personnel productivity – Nevada (1)

• Warns high-profile vehicles of high winds on 7 mile roadway segment • Environmental sensing station tracks wind speed and direction, precipitation type and rate, air temperature and humidity, and pavement temperature and condition • Central computer tracks and compares wind speeds to determine whether thresholds have been exceeded – Communicates warning messages to DMS signs along the route • Safety enhanced through reduced high-profile vehicle crashesMotorist Warning System – Florida (1)

• Provided advanced warning of slick exit ramp – System employed pavement condition and precipitation sensors and flashing beacons on static signage • On-site data processing unit activated beacons when pavement was wet • Safety improved and vehicle speeds were reduced, producing uniform traffic flow – Idaho (1)

• Warned of blowing snow on 100 mile section of roadway • Environmental sensor systems and inductive loop detectors tracked current conditions – Pavement condition, wind speed and direction, precipitation type and rate, air temperature, humidity, visibility and vehicle length and speed measured • Central computer processed data to determine whether visibility fell below established thresholds – Traffic managers alerted and determine messages posted to DMS’ • Driver behavior changes occurred, improving safety and mobility

Future Outlook – Evolution from manually activated systems to those controlled by sensor data-driven processing – In-situ anti-icing systems – Roadway closure gates – Hazard warning systems – Additional safety and mobility benefits may be expected from larger deployments – Weather-response signal timing – Variable speed limits – Enhanced winter maintenance practices – Emergence of new site-specific safety and operational applications with the advances in weather sensor technologies. – Increased use of weather data in control and safety applications as part of the IntelliDrive framework

Conclusions – Sensor data employed in a variety of applications – Some automated, others not – Safety and mobility have been enhanced by these data and applications – Many applications remain site-specific – Systems have been effective at addressing specific concerns – As sensors improve in accuracy and reliability, more widespread applications possible

References1 Federal Highway Administration. Road Weather Management Program. United States Department of Transpor-tation, 2009. http://ops.fhwa.dot.gov/Weather/ Accessed August 5, 2009.2 Center for Transportation Research and Education. Concept Maintenance Vehicle. Iowa State University. http://www.ctre.iastate.edu/research/conceptv/index.htm#phaseiv Accessed August 5, 2009.3 Roosevelt, Daniel. A Bridge Deck Anti-icing System in Virginia: Lessons Learned From a Pilot Study. Virginia Transportation Research Council, June, 2004. Available at: http://www.virginiadot.org/vtrc/main/online_re-ports/pdf/04-r26.pdf 4 Hart, Robert D., John J. Mewes, Benjamin W. Hershey, Leon F. Osborne Jr., and David L. Huft. An Overview of Implementation and Deployment of the Pooled Fund Study Maintenance Decision Support System. Proceedings: Seventh International Symposium on Snow Removal and Ice Control Technology. Indianapolis, Indiana, June 2008.

Weather Adaptive Traffic Control: Practice, Technology, and Future OutlookAhmed Al-Kaisy, Ph.D., P.E. Associate Professor, Civil Engineering Department Program Manager, Safety and Operations, Western Transportation Institute Montana State University, Bozeman, MT

David Veneziano, Ph.D. Research Scientist Safety and Operations, Western Transportation Institute Montana State University, Bozeman, MT

RWIS site - Image source: WTI

Mobile Pavement Temperature Sensor - Image source: http://www.hoosierco.com/Mobile_Temperature_Sensor_999J_e.html

Fixed Anti-icing Spray Technology system - Image source: http://ops.fhwa.dot.gov/Weather/best_practices/NYCDOTanti-icingSys.pdf

Winter weather and signal control - Image source: WTI

Maintenance Decision Support System– Image source: WTI

Web-based weather information for travelers - Image source: http://www.wsdot.wa.gov/Traffic/weather/

Winter Variable Speed Limit - Image source: http://www.wsdot.wa.gov/Regions/NorthCentral/projects/US2/StevensPass-VariableSpeed/Photos.htm

Wind Warning System - Image source: http://www.westerntransportationinstitute.org/documents/reports/426705_TM3.pdf

Icy Curve Warning System - Image source: WTI