MOOSE DETECTION DISTANCES ON HIGHWAYS AT NIGHT
Moose-vehicle collisions are a serious concern in many areas of North America and Fennoscandia. In northwestern Ontario, more than 400 moose-vehicle collisions occur annually, and 26 fatal collisions have occurred over the last 10 years. To avoid colliding with a moose, a motorist must: (1) successfully see or detect the presence of the animal; (2) determine whether or not the moose poses a threat requiring evasive action; (3) determine what action, if necessary, is required; and (4) implement the action. Whereas perception reaction times of motorists have been studied in detail, allowing calculations of post-detection distances travelled by a vehicle at different speeds, distances at which a moose can first be seen by a driver at night are unknown. We used a full-size moose decoy to determine the distances at which an animal could be detected at night when it was positioned on each shoulder and in the middle of a highway using high and low beam headlamp settings of different vehicles. Overall, we found the mean detection distance across all vehicle types, headlamp settings, and moose decoy location to be 105 m (range: 23-210 m). Headlamp setting was a significant factor; on the low beam setting, mean detection distance was 74 m and on the high beam setting it was 137 m. Moose decoy location was also important; combining the data for both headlamp settings, mean detection distances were 89 m, 93 m, and 133 m for the left, right, and centre positions, respectively. There was no relationship between headlamp height of different vehicles and moose detection distance. Comparing our results with previously known preception-reaction times of motorists, we determined that drivers travelling at night in excess of about 70 km/h are very likely to be overdriving the illumination capabilities of their headlamps for moose encounters. For drivers using a low beam headlamp setting, the maximum safe speed drops to about 60 km/h and on high beam setting, rises to about 80-90 km/h. These results suggest that along highway corridors where collisions with motor vehicles present a serious threat to public safety and may have significant impacts on local moose populations, speed limits should be set no higher than 70 km/h at night.
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