The Colorado Department of Transportation is inspecting 42,000 guardrails across the state after some were found to be installed incorrectly.

CDOT says during an accident this summer on I-25 near Johnstown, a woman's car was impaled by the guardrail that was supposed to deflect the vehicle.

She suffered significant injuries and an investigation determined the guardrail was replaced a couple years ago after an earlier crash.

When CDOT maintenance crews replace a broken or missing part of a guardrail, the parts would come from a stockpile of different manufacturer's supplies. The pieces would fit, but not work as designed.

Now CDOT is inspecting thousands of the barriers.

"So far of the 50 percent that we've looked at, which is about 20,000, we have uncovered about 144 incompatible installations," CDOT Executive Director Shailen Bhatt said.

CDOT says it is replacing the guardrails that were repaired incorrectly. They could finish the statewide work by next week.

The department is also looking into changing protocol to inspect repairs after they are done.