Effects of Tree Canopy on Pavement Condition, Safety and Maintenance - Phase 2

Tree canopies are common alongside and above rural highways in Ohio. Consequently, Ohio Department of Transportation (ODOT) wants to know how a tree canopy affects pavement condition and road safety. A review of published research conducted for Phase I of this study suggested that tree canopies extend the life of asphalt pavement and improve road safety. Road managers and highway officials said roadside trees were believed to negatively impact the pavement surface directly below the canopy, according to the report’s survey and anecdotal accounts. These impacts included increases in moisture and temperature variation, reductions of pavement longevity, and undermined road safety. These observations have not been rigorously verified, and there is a lack of prior research on the topic. This study seeks to determine if tree canopies affect asphalt pavement in Ohio, quantify any effects, and recommend best management practices. The research was approached with controlled experiments on small plots concerning microclimate and pavement condition and observations and measurements on in-service pavements covering microclimate, pavement condition, and safety. The net results show tree canopies substantially reduce thermal loading, snow accumulation, and moisture in light to moderate rainstorms. Canopies also increase the persistence of moisture on stretches of shaded pavement. Snow and ice persistence were controlled by drainage and compaction by traffic, rather than the presence of tree canopies. In addition, a negative relationship exists between pavement surface texture and tree cover, landscape position, and traffic loading, but the effects on surface texture were apparent only under unusual conditions. No significant effects on pavement cracking were found. Crash data showed improvements in safety that can be attributed to roadside maintenance activities (trimming and pruning), but not specifically to the removal of tree canopy. There were no conclusive effects to driving behavior that can be related to tree canopy cover. Consequently, this report concludes that neither pavement condition nor driving behavior should be considered sufficient justification for removal or pruning of tree canopies as a form of routine maintenance on Ohio’s rural roadways.

• Record URL:
  http://www.dot.state.oh.us/Divisions/Planning/SPR/Research/reportsandplans/Reports/Final%20Reports/FR_135566.pdf
• Record URL:
  https://ohiomemory.org/digital/collection/p267401ccp2/id/19713/rec/1
• 
• Summary URL:
  http://www.dot.state.oh.us/Divisions/Planning/SPR/Research/reportsandplans/Reports/Final%20Reports/FS_135566.pdf
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/58715
• Corporate Authors:

  Ohio University, Athens

  Department of Civil Engineering
  Athens, OH  United States  45701

  Ohio Department of Transportation

  Columbus, OH  United States  43216-0899

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Naik, Bhaven
  • 0000-0003-0436-885X
  • Matlack, Glenn
  • 0000-0002-9628-0937
  • Khoury, Issam
  • 0000-0003-4856-7535
  • Sinha, Gaurav
  • 0000-0002-1280-6269
  • McAvoy, Deborah S
  • 0000-0002-0411-0034
  • Horn, Andrea
  • Gassaway, O Ryan
• Publication Date: 2020-9

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Maps; Photos; References; Tables;
• Pagination: 214p

Subject/Index Terms

• TRT Terms: Condition surveys; Highway safety; Maintenance management; Moisture content; Pavement cracking; Pavement performance; Service life; Temperature; Texture; Trees
• Geographic Terms: Ohio
• Subject Areas: Highways; Maintenance and Preservation; Pavements; Safety and Human Factors;

Filing Info

• Accession Number: 01756303
• Record Type: Publication
• Report/Paper Numbers: FHWA/OH-2020-17
• Contract Numbers: SJN: 135566; PID: 105899
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Oct 27 2020 5:48PM