No mitigating effects of roadside vegetation clearing on ungulate-vehicle collisions in Nord-Trøndelag

The number of ungulate-vehicle collisions has increased substantially over the last few decades. To reduce the number of accidents several mitigation measures have been implemented, but there is in many cases no evaluation of their collision preventive effect. By analysing moose (Alces alces) and roe deer (Capreolus capreolus) collision data from 2009 2015, I evaluated the effect of roadside vegetation clearing conducted in 2011 and 2012 in Nord-Trøndelag in central Norway. In the cleared areas I expected a substantial decrease in collision probability in the year after a clearing, followed by a slow increase as the vegetation re-emerged. I found that for both species the probability of a collision was substantially higher in cleared versus uncleared areas, indicating that the areas with high risk of collisions are targeted for vegetation clearing. However, the results revealed no reduction in the number of roe deer and moose collisions following clearing, indicating that vegetation clearing has no collision preventive effect. For moose, I found the number of collisions on cleared and uncleared stretches to be synchronised among years, and that the annual growth in collision numbers and snow depth were positively correlated. This suggests that snow depth is an important factor influencing the number of moose-vehicle collisions in Nord-Trøndelag