A Rock Chip on I-40 or I-85: What to Do in the First 24 Hours

Why this stretch of road throws so many stones

Between Raleigh and Hillsborough, I-40 runs past RDU and I-540, through Research Triangle Park, along the south of Durham and the north edge of Chapel Hill, then meets I-85 on Hillsborough’s southern outskirts. I-85 crosses the north of Durham. Both carry heavy trucks, and both have had long stretches of road work. Most chips come from a stone thrown up by a tire or blown off a load in front of you.

North Carolina law already asks for loads to be secured. G.S. 20-116(g) says no vehicle may be driven on a highway unless it is loaded to keep anything from falling, blowing, dropping, sifting or leaking off, and trucks over 7,500 pounds carrying rock, gravel or stone must keep the load six inches below the sides and covered by a tarpaulin or similar cover. That reduces the problem; it does not end it.

In the first few minutes

• Keep driving normally until you can stop safely. A chip is not a reason to swerve or brake hard.
• When you stop, look at where it is: near the edge of the glass, in front of the driver, or behind the mirror where the camera looks out.
• Put a piece of clear tape over it. It keeps out dirt and rain, which can stop resin bonding cleanly later.
• Take a photo with a coin beside it. That one picture tells a technician most of what they need to know.

The rest of the day: the mistakes that turn chips into cracks

A chip is a weak spot in the outer layer of the glass, and stress gathers there. The usual causes of a chip running into a crack are quick changes in temperature and sharp jolts. So for the first day:

• Do not blast the defroster or the air conditioning straight at the glass. Change the cabin temperature gradually.
• Skip the car wash, especially cold water on glass that has been in the sun.
• Close the doors gently. A slammed door pushes air against the inside of the glass.
• Slow down for potholes and rough patches.
• Leave more room behind trucks for the rest of the drive. Lightning does strike twice on a gravel route.

Repair or replace: a quick check you can do yourself

Impex’s rule is that a repair may be possible when the damage is small, shallow and away from the edges of the glass. The industry repair standard, ROLAGS, treats stone breaks up to two inches across and single line cracks up to 14 inches as repairable. A common rule of thumb is that a chip smaller than a quarter can usually be filled. If yours fits, the job is a resin repair, covered on our page on windshield repair Durham.

If a crack is already running toward the edge, if the damage is right in front of the driver, or if there are several breaks, it is likely to need a new windshield. That job, with the camera calibration many newer cars need afterwards, is on windshield replacement Durham NC.

Is a chip a problem at inspection?

North Carolina’s annual safety inspection under G.S. 20-183.3 checks your windshield wipers, not the glass itself, and no NC statute sets a crack size. So a chip is not an inspection item. That is not a reason to leave it: the windshield is part of the car’s passenger restraint system, and a crack in your line of sight is a safety problem in its own right.

Who pays

Glass damage from a flying stone is a comprehensive loss in North Carolina, paid less any deductible. Many chip repairs cost less than the deductible, so drivers often pay directly. If your policy has full glass coverage, check what it says about repairs. Either way, under G.S. 58-3-180 you choose who does the work.

The short version: tape it, photograph it, keep the temperature steady, and get it looked at within days rather than weeks.

Questions people ask