Why Do Some Road Signs Have Holes in Them?

In some rural parts of the country, coming to a traffic stop can reveal a peculiar feature on road signs: holes. Lots of holes. It’s no great leap in logic to assume they were made by a bored firearms owner who decided to use the sign for target practice. But vandalism isn’t the only reason a traffic sign might have holes in it.

Why Some Street Signs Have Holes

If a street sign has a series of erratic holes of varying sizes that remind you of a shot-up T-1000 in Terminator 2, it’s likely the result of bullets penetrating the aluminum. (More on that in a moment.) But if the holes appear arranged and cleanly perforated, the sign has likely been manufactured with a clear objective: reducing wind resistance.

Some parts of the country are prone to winds strong enough to take down everything from awnings to power lines. A traffic sign may not stand a chance. If a sign is carried away, it can create serious safety issues, particularly if it flies into a crowd of people or breaks a car window. To keep the sign in place, some counties in flat or coastal areas will have them perforated so the wind can pass through.

Though the practice isn’t common across the U.S., there’s been research into its efficacy. A 2020 study published in the journal PLOS One examined how different perforation patterns might reduce wind resistance. (Holes ranging in size from 30 millimeters to 60 millimeters appear to work best, with spacing four to five times the hole radius, in case you were wondering.)

You might see these holes either in signs anchored to the ground or attached to traffic light poles. In some cases, the traffic lights themselves may sport perforations for the same reason.

Bullet Holes in Traffic Signs

Bullet holes remain a fixture of some traffic signs, which can cause headaches for residents and local governments. In West Fargo, North Dakota, vandals shooting up signs caused upwards of $15,000 in damage in 2019, which wound up being a burden for taxpayers. In the state, it’s estimated counties need to replace 50 percent of their signs annually owing to illegal target practice.

In addition to being a financial drain, shooting signs is, of course, inherently dangerous. The more holes in a traffic sign, the more obscured its message, which jeopardizes motorists. Holes can also reduce a sign’s reflectivity, making it unreadable at night. In North Dakota, some auto accidents have been blamed in part on vandalized signs.

Ironically, new signs can prove to be the most tempting for shooters, since their shiny surface makes for an easier target. But there’s always a chance a bullet intended for a no-left-turn sign winds up in someone’s house or worse. While vandalism isn’t usually a serious crime, a defaced sign leading to a tragedy could land the vandal with more severe charges.

The lesson? If your community needs to build signs for windy conditions, it’s best to leave the holes to the manufacturer.

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