Reducing Overheight Collisions: Where and Why They Occur

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Did you know that in an Alaska Department of Transportation (DOT) survey of 29 U.S. states, 18 indicated that they consider overheight collisions a significant problem?

In fact, Maryland identified 1,496 bridges susceptible to overheight impacts across the state, with 309 (20 percent) having been struck at least once. Some low-clearance structures, like a rail bridge in Durham, North Carolina, even average over one strike per month.

Unfortunately, these collisions can result in serious injuries and fatalities, though no nationwide database exists to track how many.

Overheight collisions also cost governments millions of dollars each year. One damage-causing strike can decimate the budget of a city or roadway authority. According to a Texas DOT study, the average cost of an overheight collision can range from $200,000 to $300,000. That doesn’t even include the associated costs of local traffic congestion, new route planning and insurance premium hikes.

In addition, because many overheight collisions are hit and runs, identifying the culprit and holding them accountable is a tall order.

The first step to combating this dangerous problem is understanding it, so I've laid out where and why overheight collisions happen below.


Where Overheight Collisions Occur

Overheight collisions most commonly occur at low-clearance structures like:

  • Low bridges
  • Weigh stations
  • Parking structures
  • Tunnels
  • Underpasses
  • Airports
  • Manufacturing facilities

Why Overheight Collisions Occur

There are five factors that cause most overheight collisions:

  1. Drivers unaccustomed to driving tall vehicles, such as a couple renting a box truck to move into a new home, may fail to account for a low-clearance structure in time.

  2. Professional drivers in unfamiliar territory may accidentally deviate from the path laid out by their GPS, causing them to encounter unexpected low-clearance structures.

  3. Because truck heights vary based on load weight, inexperienced truck drivers may forget about their varying vehicle height.

  4. Distracted and/or tired drivers are less likely to notice static overheight warning and clearance height signs, especially at night. By the time they become aware of an impending collision, it may already be too late.

5. Railroad bridges built before motorized vehicles were not designed with trucks in mind, especially on arterial and local roadways. Therefore, they tend to be lower, catching some drivers off guard.

Understanding where and why overheight collisions occur enables traffic safety professionals to make better decisions about how to reduce them and safeguard lives.


Learn how to select the right overheight warning solutions our free how-to guide >


Part 2: Identifying Structures in Need of an Overheight Solution

Part 3: Get to Know Your Overheight Warning System Options

Kate Bert

TAPCO | Product Manager

Kate is a wrong-way alert and overheight warning systems expert dedicated to providing customers with innovative products, knowledge and guidance.

She has extensive experience in engineering, operations and product management and is passionate about collaborating with the team to develop lifesaving solutions to ensure safe travel for all users.

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