Gov. Scott Walker favors a surcharge on hybrid cars rather than increasing the user fee on gasoline.
The science shows a surcharge should be put on heavier cars and trucks, which are now being subsidized by the hybrids. Tests that highway engineers did on the impact of vehicle axle weight to road wear and tear found it varies by the ratio of the weights to the fourth power.
Let us use an example of a Ford Fusion (the hybrid), and the Ford Expedition. The ratio of the weights of the Expedition to the Fusion is about 1.6, and, applying the fourth power law, the Expedition produces about 6.5 times the road wear and tear of the Focus per mile driven.
The Expedition gets about 21 mph, while the Focus gets about 42, so the Expedition pays twice as much per mile in gasoline user fees than does the Focus owner, though it causes 6.5 times the damage.
The Focus owner is thus subsidizing the Expedition owner. The roads of Wisconsin are in terrible shape, and the owners of heavier vehicles should pay their fair share.
John Reindl, Madison, retired professional engineer
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