Why Michigan is so prone to potholes - and why repairs seem ineffective

Pothole season in full effect for Michiganders

DETROIT - Potholes have become a Michigan tradition - not one we enjoy keeping alive.

Potholes have been particularly bad in recent years. It's been so rough, we stopped asking for the worst potholes and started asking for the best roads in Metro Detroit.

So what's the deal with potholes? Why are they so bad in Michigan? The simple answer is: it's our crazy Pure Michigan weather.

Pothole questions: Why are Ohio's roads better than Michigan's roads?

Potholes are created when snow and ice melt as part of Michigan's seasonal freeze-thaw cycles. Moisture seeps into the pavement, freezes, expands and thaws, creating a gap in the pavement. As vehicles drive over the gap, the pavement weakens leading to a pothole.

So, in a month where we can have ten inches of snow and three inches of rain in a three-week span, potholes are thriving on Michigan roads.

What's up with pothole repair?

It may seem that pothole repair is messy and ineffective. You may hear that the potholes will be fixed temporarily - with the intention of repairing the road during the summer months.

Why fix it twice?

Here's some great insight from Pothole.info:

The answer is in the nature of asphalt formulations – there are many – and how winter weather makes road repairs difficult all around. That said, there are newer types of asphalt and methods that overcome the challenges of ice, snow and cold temperatures – fixing roads faster and probably reducing overall costs (there are several variables). This gives motorists and taxpayers something to cheer.

To understand why there is this pothole repair two-step, it helps to look at the different formulations for the binder – which in the trade is referred to as “asphalt cement,” the black gooey stuff that the holds the rocks and sand (“aggregate”) together. And even the aggregate itself can vary from region to region, affecting the binder. Most binder is hot-mix asphalt (HMAs), but there are also cold-mix asphalts (CMAs). The use of each roughly corresponds with the seasonal temperatures: HMA in summer, CMA in winter.

To achieve a more resilient, permanent asphalt road, the all-important physical task in this process is compaction. A mix laid down into a pothole, for example, will be more permanent if the air between the aggregate and binder is minimized (7% air voids or less). Rolling a heavy truck tire or rollers over newly laid asphalt, or by way of hand-held tampers, is the primary means for achieving that compaction.

But it’s not solely dependent on the brute force of pressing the asphalt together. With hot-mix asphalt, that compaction has to be done while it’s still hot. If the mix has cooled before compaction, as will happen in colder weather, there will be more air voids. Which is why permanent pothole repairs are generally done in warmer weather. It’s not only difficult to keep the asphalt mix hot after leaving the asphalt plant, in many markets where winter is long and cold the asphalt plants simply cease operations during winter.

This is why most potholes get a temporary, loose aggregate of cold mix asphalt. In some cases, the road maintenance crew fixes potholes with a simple “throw and go” treatment. There may be a small amount of compaction achieved with the back side of a shovel, but the first cars and trucks to run over relatively loose piles of asphalt filler are the primary method to tamp down the mix.

But that same traffic is also what leads to further deterioration in a relatively short time. The net result is potholes return quite quickly – within days or weeks.

There are better quality cold mix asphalt formulations available. They typically cost more, but the savings come from a single, versus double, pothole repair. This is why one city might have better roads than another nearby.

How to drive through potholes

It's unfortunate that we have to note this, but here's what MDOT suggests:

There are often two schools of thought on driving through potholes: speeding up to "jump" over them and jamming the brakes hard to hit them as slowly as possible. Both might work occasionally but the best way is somewhere in between. 

If you see a pothole ahead and can't safely steer to avoid it, it's best to slow down, then release the brakes before you hit the pothole. This helps to reduce the speed at impact as well as give your suspension the full range of travel to absorb the impact.

If you can't avoid the pothole, straighten your wheel to hit it squarely and roll through. Hitting a pothole at an angle can transfer the energy of impact in ways more likely to damage your vehicle.

How to report a pothole

Whether you hit a pothole or you missed it, you can save your fellow motorists the headache and costs of repairs by reporting it. If it's on a city street or county road, report it to your city public works department or county road commission.

If it's on state trunkline (I, M or US route), submit it to MDOT's Report a Pothole webpage or call it in to the Pothole Hotline at 888-296-4546.

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