Arboriculture & Urban Forestry 45(2): March 2019 Arboriculture & Urban Forestry 2019. 45(2):65–74 URBAN FORESTRY ARBORICULTURE Scientific Journal of the International Society of Arboriculture & Frequency and Severity of Tree and Other Fixed Object Crashes in Florida, 2006–2013 Jeffery W. Van Treese II, Andrew K. Koeser, George E. Fitzpatrick, Michael T. Olexa, and Ethan J. Allen Abstract. Roadside trees provide benefits to drivers such as traffic calming, roadway definition, and driver stress reduction. However, trees are also one of several roadway infrastructure elements commonly involved in single-vehicle crashes. In this study, Florida Highway Saftey and Motor Vehicle records were analyzed to: evaluate the relative frequency of tree-related crashes compared to other fixed-object crashes; assess the impact of roadway-, vehicle-, and driver-related factors on tree crash frequency; and compare the severity of tree crashes relative to other single-vehicle crashes. In accessing 3,033,041 crash records from 2006 to 2013 (all complete years), we identified 323,581 single-vehicle acci- dents (10.6%) and 47,341 tree-related accidents (1.6%). Trees were the third most common fixed object hit in urban single-vehicle accidents and the second most common fixed object hit in rural single-vehicle accidents. Driver gender, vehicle type, light conditions, weather conditions, and land use all were correlated with the frequency. Additionally, the injuries associated with tree crashes were more severe than all other single- vehicle crash types except vehicle rollovers. Key Words. Risk; Single-Vehicle Collisions; Transportation; Tree Hazards; Urban Forestry. 65 INTRODUCTION Risk is a combination of the probability of an event occurring and the consequence of the event should it occur (Frank and Bernanke 2004). When urban forest- ers and other professionals assess tree risk, they typi- cally focus on the probability that a tree (or part of a tree) will fail and strike a target such as a person or prop- erty. Smiley et al. (2011) describes a tree as hazardous if it has both a structural defect that predisposes the tree to failure and a target that would be struck if it were to fall. Smiley et al. (2011) goes on to say that healthy trees may be hazardous if they obstruct a motorist’s vision, raise sidewalks, interfere with utilities, or are particularly attractant to lightning. To the extent trees are evaluated as roadside hazards, research in arboriculture and urban forestry has been limited to the risk posed by a tree or branch should it fall on, or immediately in front of, a passing vehicle (Ellison 2005; Rooney et al. 2005; Laefer and Pradhan 2006; Klein et al. 2016). In contrast, research from transpor- tation and planning has largely focused on trees and their potential involvement in fixed-object vehicle crashes (Zeigler 1986; Turner and Mansfield 1990; Lee and Mannering 1999; Naderi 2003; Dumbaugh 2005; Holdridge et al. 2005; Dumbaugh 2006; Mok et al. 2006; Wolf and Bratton 2006; Abdin et al 2009; Park and Abdel-Aty 2015). Roadside vegetation is a significant component of roadway planning. Between 2008 and 2013, the Flor- ida (United States) Department of Transportation spent $209 million on highway landscaping (Khachatryan et al. 2014). This roadside beautification led to $46 million in annual output impacts (total state expendi- ture) and $28 million in annual value added impacts (wages, increased property income, proprietor income, indirect business taxes, and capital consumption) (Khachatryan et al. 2014). While harder to quantify than the economic benefits noted above, tree-lined roadsides increase the aesthetic appeal of streetscape vegetation, reduce driver stress, and facilitate a more pleasant driving experience when compared to more barren streetscapes (Wolf 2003). These benefits may be especially important for drivers who become frus- trated with traffic congestion and long commutes ©2019 International Society of Arboriculture
March 2019
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