Does road salt make winter driving safer?

Given the lack of progress since Madison first tried to reduce road salt use, it's time to look for new ways of viewing the problem.

As soon as a conversation about salt begins, the subject of winter road safety comes up.  Road safety seems to override any other argument.

But does salt really make winter driving safer?  We can refine this question to ask... "Do the obvious safety benefits of salt outweigh the enormous economic and environmental damage caused by salt?"

"Outweigh" implies that we have to measure--to quantify--both the benefits and costs of salt.

An obvious starter...  Are there any highway accidents actually caused by salt?

A bridge collapses

The answer is yes.  The St. Anthony Falls Bridge (I-35W) in Minneapolis collapsed in 2007, killing 13 and injuring 145.  The primary cause found was a design flaw which weakened the bridge.  A secondary cause was loading the bridge with construction equipment.

De-icing solutions applied to the bridge were also implicated.  After experimenting with highly corrosive magnesium chloride, they settled on an automatic system for spraying potassium acetate,"...which may have contributed to the collapse of the 35W bridge by corroding the structural supports." "In 1990, the federal government gave the I-35W bridge a rating of "structurally deficient," citing significant corrosion in its bearings."  At that time, the bridge was only 23 years old.  Source
In Madison, we have more parking ramps than bridges.  If the concrete cracks, salt dripping from wheels can penetrate to the reinforcing rods.  If those rust, the ramp could collapse.  Imagine all those autos, flat as a pancake.

Corrosion causes traffic accidents

About 20 years ago, I had to junk a car because of severe rust.  The hood kept popping up--due to a defective latch, I thought.  When I took it in to have the latch fixed, the mechanic said the real cause was the chassis rusting loose from the front wheels.  The whole car was settling down--causing the engine to push up against the hood.  He said the car would soon drop completely onto the front wheels, causing the steering to suddenly lock.  I hadn't realized I was so close to a serious accident--caught just in time.

A year ago, I saw an accident in Madison probably caused by corrosion.  On Midvale Blvd, the fuel tank on a semi truck broke loose, dragging the tank and spilling fuel for a half mile along the street.  If this had happened at 75 mph, sparks from the dragging tank could have ignited the fuel.  Salt corrodes gas tanks.  Salt gets under the tank attachment strap, making it hard to wash off.

Was this accident caused by poor maintenance, driver error, or corrosion due to salt?

Causality issues

Even after long analysis of the bridge failure, it's hard to say how much of it was due to corrosion from de-icing compounds.  There was a tendency to downplay the record of inadequate inspection of the bridge.  It was easy to blame the designer for the design flaw, because that had happened long ago.

An engineer would say contributing causes are just that--one of the causes.  How much blame to assign to the salt isn't an exact science.

When a driver spins off the road because the road hasn't been cleared of ice--do you blame to the driver for going too fast, or do you blame the City for failing to clear the ice?  The driver would like to blame the City.  It's really a question of commonly accepted views of responsibility.  Since salting began in the early 1950s, responsibility for safe winter driving has been gradually shifting to government.

In conclusion, since salt is so often a contributing factor, it doesn't get its real share of blame for accidents and environmental damage.  When the police investigate an accident, they aren't going to say "this was due 60% to corrosion from to salt.  At best they'll call it "mechanical failure."

Although the poisoning of Flint's water supply is in the news, you won't hear in many news stories that road salt played a role in corroding the pipes, releasing the lead.

But when it snows and roads aren't cleared fast enough, you hear a lot of complaints.  People can see the snow--the corrosion is nearly invisible.

Salt isn't as safe as we thought.

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Photos: Corrosion of Chicago's bridges
Photos: Fuel spill from dragging fuel tank on Midvale Ave.


  1. Hi! I really like rivers and creeks. I just moved to Madison and am having a hard time locating some of the creeks in town. Where would you recommend that I go to find a list of moving water in town?

  2. Do you want to paddle? Try Mad City Paddlers. Places to paddle: Perhaps best (a short paddle) is Pheasant Branch Creek at NW end of Lake Mendota. Cherokee Marsh (the Yahara River) at N. end of L. Mendota. Try Yahara River from Tenney Park, to Lake Monona. You can take the yahara River south from Lake Monona through Mud Lake to Lake Waubesa. South of Madison at Belleville is the Sugar River, great for canoeing. The Wisconsin River west of Madison is nearly wild and great for camping on sandbars and canoeing or kayaking. The stretch from Sauk City to Spring Green is a day's trip and good for a starter. Try Devil's Lake 50 min NW of Madison.

    Not sure where to go online, except to find a good map. Try the WI Natural History Survey office on Mineral Pt. rd, just west (on S side) of the intersection of Mineral Pt. rd and Speedway.


Please feel free to comment on the article above, or on other watershed issues.