If you get caught in a snowdrift over the next year or two, don't blame J.D. Iversen. The Iowa State University professor of aerospace engineering has been hard at work probing the mysteries of drifting snow and of how to keep it from piling up on the nation's highways.
His conclusion: Plants or even guardrails along road shoulders tend to increase drifting. For maximum snowdrift control, he says, there is nothing like a flat landscape with no trees, billboards, crops, or overpasses to block the flow of snow as it moves across the road. The only place where plantings or similar obstacles may help rather than hinder: overpasses. There, if placed close together some distance from the highway on the windward side of the overpass (usually north or northwest in winter), they can cut down on road drifts.
To come up with that advice for roadbuilders, Dr. Iversen first looked at the wind movement of dust and sand on Mars by studying photos taken by the Mariner 9 and Viking spacecraft. Wind effects were very marked, he says, despite the fact that the planet's lower atmospheric density requires a windspeed about 10 times that of Earth for the same results.
To pin down more precisely the physics of blowing particles on Earth, Iversen and ISU civil engineering Prof. S. L. Ring, under an Iowa Department of Transportation grant then built a new wind tunnel and tested the wind action there with simulated snow.
One problem was trying to simulate snow. Crystals of instant tea proved too fine and powdery for the job. Ground walnut shells were carried higher than snow by the wind and hung in the air rather than floating to ground. Minute glass beads proved the best snow substitute. Carrying an electrostatic charge, they formed drifts remarkably like those encountered by motorists.
Iversen says Iowa road officials have already made use of the findings to some degree by removing some of the bushes planted close to Interstate highways. ''But highway funds right now are kind of scarce,'' he stresses.