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Low-clearance bridge alerts
Learn where bridge-clearance data comes from, what alerts can and cannot tell you, and how to use them safely.
Where the data comes from
Terrapin uses records from the Federal Highway Administration’s National Bridge Inventory, which is updated periodically. The app checks more than 66,000 bridge records with clearance measurements relevant to truck travel. For each route, Terrapin identifies nearby bridge records and compares their recorded clearances, after applying a six-inch safety margin, with your vehicle’s height.
Why alerts say “possible”
- A clearance record may refer to a different roadway, such as a road passing beneath a bridge.
- Some records may be outdated, and the inventory does not cover every overhead obstruction.
- Road resurfacing and other changes can affect actual clearance. Posted signs and current road conditions take priority.
Treat every alert as a reason to verify the clearance ahead. An alert is not a guarantee that a route is safe or unsafe. Always follow posted signs and use your vehicle’s actual measured height.
Vehicle height and legal limits
Maximum legal vehicle heights vary by state and route. Many states commonly permit vehicles up to 13 feet, 6 inches, but some allow different heights. Rental box trucks may be shorter. The table below shows published clearance heights for selected rental models.
| Truck | Published clearance | Source |
|---|---|---|
| U-Haul 10 ft | 9 ft | U-Haul truck page |
| U-Haul 15 ft and 20 ft | 11 ft | U-Haul truck pages |
| U-Haul 26 ft | 12 ft | U-Haul truck page |
| Budget 12 ft | 9 ft | Budget truck page |
| Budget 16 ft | 11 ft | Budget truck page |
| Budget 26 ft | 13 ft | Budget truck page |
| Penske 26 ft straight truck | 13 ft 6 in | Penske FAQ |
Figures are based on rental-company information reviewed in October 2026. Actual vehicles may vary. Check the specific truck’s label and measure its height before traveling.
Using Terrapin
Enter your vehicle’s measured height in Terrapin. The route summary displays possible clearance conflicts, and the app provides a spoken warning approximately one mile before an identified hazard. See all features or request early access.