Implementation Process: Appendix G-2
Example Table of Crash Attributes vs. Candidate Strategies for Crashes involving Trees in Hazardous Locations
Exhibit 1 is an index of candidate strategies for addressing crashes involving trees. The strategies listed are those that are covered in the Guide for the AASHTO Strategic Highway Safety Plan addressing crashes involving trees in hazardous locations. Please note that in many cases, sites with tree crashes problems may be amenable to correction using strategies designed to keep a vehicle on the road. Strategies designed to mitigate run-off-road crashes may be found in the Guide for Addressing Run-Off-Road Accidents of the AASHTO Strategic Highway Safety Plan.
In many cases, roadway inventory data may be available as an additional source to help relate problems to candidate strategies. Where the scope of the analysis is limited to a relatively small portion of the road system, field studies can provide needed details to help select the appropriate strategies to consider. Other sources of data are sometimes available, as well, which can help in the analysis. Details of the problem identification process are covered in the discussion of Step 1 of the Model Implementation Process.
All of the strategies listed in the guide for tree crashes are potentially applicable to several of the crash factors. Even where this is not the case, it may occur that more than one crash factor will be identified as significantly associated with the problem. In these cases, the sum of strategies associated with each of the factors, as listed in Exhibit 1, should be considered. For example, if the analysis suggests that there is an overrepresentation of both run-off-road crashes and vehicle striking trees planted on a non-recoverable slope, then one should study the application of not only the strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide, but also Strategy 16.1.2.3 (Modify Roadside Clear Zone in the Vicinity of Trees) in the guide for tree crashes, as well as such strategies as 16.1.2.1 and 16.1.2.2 which deal with removing the trees or shielding motorist from striking trees.
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Exhibit 1 – Linkage Between Crash Factors and Candidate Strategies |
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Crash Factors |
MMUCC Element No. or Other |
Candidate Strategy |
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Contributing Road Factors |
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Run-Off-Road |
C6 |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide |
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Collision with a Fixed Object – Tree |
C6 |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide
16.1 A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations
16.1 B1 - Remove Trees in Hazardous Locations
16.1 B2 - Shield Motorists from Striking Trees
16.1 B3 - Modify Roadside Clear Zone in the Vicinity of Trees
16.1 B4 - Delineate Trees in Hazardous Locations (experimental) |
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Nature of Crash |
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Run Off Road Striking Trees in the Median |
C6, C7,V23, Site Investigation |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide
16.1 A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations
16.1 B1 - Remove Trees in Hazardous Locations
16.1 B2 - Shield Motorists from Striking Trees
16.1 B4 - Delineate Trees in Hazardous Locations (experimental) |
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Run-Off-Road and strike a tree on a side slope |
C6, V23, Site Investigation |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide
16.1 B1 - Remove Trees in Hazardous Locations
16.1 B2 - Shield Motorists from Striking Trees
16.1 B3 - Modify Roadside Clear Zone in the Vicinity of Trees
16.1 B4 - Delineate Trees in Hazardous Locations (experimental) |
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Crashes Involving Intentionally planted Trees |
C6, V23, Site Investigation |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide
16.1 A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations |
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Crashes Involving Tree Encroaching the Roadway |
C6, V23, Site Investigation |
Apply Strategies in the AASHTO Strategic Highway Safety Plan Run-Off-Road Guide
16.1 A2 - Mowing and Vegetation Control Guidelines |
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Crashes Involving Trees Creating Overhead Hazards |
C6, V22, Site Investigation |
16.1 A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations
16.1 A2 - Mowing and Vegetation Control Guidelines |
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Crashes with Objects Visually Obstructed by Trees |
C14, Crash Narrative, Site Investigation |
16.1. A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations
16.1 B1 - Remove Trees in Hazardous Locations
16.1 A2 - Mowing and Vegetation Control Guidelines |
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Crashes with trees or limbs in the road |
C6, C14, |
16.1 A1 - Develop, Revise, and Implement Planting Guidelines to Prevent Placing Trees in Hazardous Locations
16.1 B2 - Mowing and Vegetation Control Guidelines |
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