A Spatial Cluster Analysis of Tractor Overturns in Kentucky from 1960 to 2002

PLoS ONE, Published 24 January 2012

Daniel M. Saman, Henry P. Cole, Agricola Odoi, Melvin L. Myers, Daniel I. Carey, and Susan C. Westneat

“Background: Agricultural tractor overturns without rollover protective structures are the leading cause of farm fatalities in the United States. To our knowledge, no studies have incorporated the spatial scan statistic in identifying high-risk areas for tractor overturns. The aim of this study was to determine whether tractor overturns cluster in certain parts of Kentucky and identify factors associated with tractor overturns.

Spatial Empirical Bayes' (SEB) smoothed tractor overturn rates in Kentucky, 1960–2002.

Spatial Empirical Bayes' (SEB) smoothed tractor overturn rates in Kentucky, 1960–2002.

“Methods: A spatial statistical analysis using Kulldorff’s spatial scan statistic was performed to identify county clusters at greatest risk for tractor overturns. A regression analysis was then performed to identify factors associated with tractor overturns.

“Results: The spatial analysis revealed a cluster of higher than expected tractor overturns in four counties in northern Kentucky (RR = 2.55) and 10 counties in eastern Kentucky (RR = 1.97). Higher rates of tractor overturns were associated with steeper average percent slope of pasture land by county (p = 0.0002) and a greater percent of total tractors with less than 40 horsepower by county (p<0.0001).

“Conclusions: This study reveals that geographic hotspots of tractor overturns exist in Kentucky and identifies factors associated with overturns. This study provides policymakers a guide to targeted county-level interventions (e.g., roll-over protective structures promotion interventions) with the intention of reducing tractor overturns in the highest risk counties in Kentucky.”