Mobility and Safety Impacts of Winter Storm Events in a Freeway Environment Final Report
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MOBILITY AND SAFETY IMPACTS OF WINTER STORM EVENTS IN A FREEWAY ENVIRONMENT FINAL REPORT Sponsored by the Project Development Division of the Iowa Department of Transportation andtheIowaHighwayResearchBoard Iowa DOT Project TR-426 CTRE Management Project 98-39 February 2000 The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Iowa Department of Transportation. CTRE's mission is to develop and implement innovative methods, materials, and technologies for improving transportation efficiency, safety, and reliability, while improving the learning environment of students, faculty, and staff in transportation-related fields. MOBILITY AND SAFETY IMPACTS OF WINTER STORM EVENTS IN A FREEWAY ENVIRONMENT FINAL REPORT Principal Investigator Keith K. Knapp Assistant Professor of Civil and Construction Engineering Iowa State University Manager of Traffic Engineering and Traffic Safety Programs Center for Transportation Research and Education Transportation Research Specialist Dennis Kroeger Center for Transportation Research and Education Graduate Research Assistant Karen Giese Center for Transportation Research and Education The preparation of this report was financed through funds provided by the Iowa Department of Transportation through its research management agreement with the Center for Transportation Research and Education, CTRE Management Project 98-39 and the Iowa Highway Research Board, TR-426. Center for Transportation Research and Education Iowa State University Iowa State University Research Park 2901 South Loop Drive, Suite 3100 Ames, IA 50010-8632 Telephone: 515-294-8103 Fax: 515-294-0467 http://www.ctre.iastate.edu February 2000 i TABLE OF CONTENTS LIST OF FIGURES................................................................................................................................................ VI LIST OF TABLES............................................................................................................................................... VIII EXECUTIVE SUMMARY ......................................................................................................................................X INTRODUCTION .....................................................................................................................................................1 PROJECT BACKGROUND AND ORGANIZATION ..................................................................................................1 PROJECT PURPOSE AND NEED.............................................................................................................................1 OBJECTIVES...........................................................................................................................................................3 REPORT ORGANIZATION ......................................................................................................................................3 LITERATURE REVIEW .........................................................................................................................................4 INTRODUCTION .....................................................................................................................................................4 WEATHER AND ROADWAY CAPACITY ...............................................................................................................4 WEATHER AND VOLUME/TRAVEL DECISIONS ..................................................................................................5 WEATHER AND SPEED..........................................................................................................................................6 WEATHER AND SAFETY .......................................................................................................................................7 ROADWAY AND WEATHER CONDITION MEASUREMENTS...............................................................................7 SITE SELECTION AND DATA COLLECTION ..................................................................................................8 PROJECT PHASE I: ARCHIVED WINTER STORM EVENT DATA .........................................................................8 Site Selection Criteria ........................................................................................................................................8 Data Collection Sites Selected ...........................................................................................................................9 Data Collected ...................................................................................................................................................9 PROJECT PHASE II: PROJECT-COLLECTED WINTER STORM EVENT DATA..................................................20 Site Selection Criteria ......................................................................................................................................21 Data Collection Site Selected...........................................................................................................................22 Data Collection Preparation............................................................................................................................22 Winter Weather Data Collection Concerns......................................................................................................25 Winter Storm Event Data Collection................................................................................................................26 Post-Trip Data Collection................................................................................................................................32 SUMMARY............................................................................................................................................................32 WINTER STORM EVENT IMPACT ANALYSIS ..............................................................................................32 PROJECT PHASE I: ARCHIVED WINTER STORM EVENT DATA .......................................................................33 Winter Storm Event Traffic Volume Impacts....................................................................................................33 Winter Storm Event Crash Impacts..................................................................................................................40 PROJECT PHASE II: PROJECT-COLLECTED WINTER STORM EVENT DATA...................................................43 Winter Storm Event Speed Impact Statistical Analysis ....................................................................................47 Winter Storm Event Speed Impact Summary....................................................................................................53 APPLICATION OF RESEARCH RESULTS.......................................................................................................53 WINTER WEATHER ROADWAY USER IMPACTS AND THE FORETELL INITIATIVE...................................54 FORETELL DESCRIPTION...............................................................................................................................54 The Application of Roadway User Impacts in FORETELL ..........................................................................56 WINTER WEATHER ROADWAY USER IMPACTS AND DES MOINES/IOWA ITS STRATEGIES .......................57 Description of Strategic Plan Components......................................................................................................57 The Application of Roadway User Impacts in the Des Moines Metropolitan Area ITS Strategic Plan...........59 The Application of Roadway User Impacts and ITS Measures in Rural Iowa.................................................60 SUMMARY............................................................................................................................................................61 CONCLUSIONS AND RECOMMENDATIONS.................................................................................................62 iii CONCLUSIONS .....................................................................................................................................................62 RECOMMENDATIONS..........................................................................................................................................65 REFERENCES ........................................................................................................................................................67 APPENDIX...............................................................................................................................................................70 iv LIST OF FIGURES FIGURE 1 DATA COLLECTION SITES COLLECTED ............................................................................................... 9 FIGURE 2 AVERAGE DAILY TRAFFIC FLOW PROFILES (APRIL 1997, JEWELL, IOWA, ATR #104)................ 15 FIGURE 3 AVERAGE SATURDAY TRAFFIC FLOW PROFILE (APRIL 1997) AND WINTER STORM EVENT (APRIL 12, 1997) VOLUMES................................................................................................................. 17 FIGURE 4 ROADWAY SEGMENTS USED IN CRASH ANALYSIS.......................................................................... 19 FIGURE 5 TYPICAL TRAFFIC CONTROL PLAN FOR RURAL COUNTY ROADWAY OVERPASS........................ 22 FIGURE 6 AUTOSCOPE EQUIPMENT