The crash happened in the southbound lanes of U.S. 31 near the Pontaluna exit in Norton Shores.
Police say a 73-year-old woman from Twin Lake was northbound in the southbound lanes. Police are not sure where the woman entered the highway, but they say that several motorists called 911 before the crash to report her.
A car driven by a 30-year-old man was not able to avoid her. The collision sent his car rolling onto the shoulder of the road. He was taken to the hospital with serious injuries.
The woman was not hurt, but was taken to the hospital as a precaution.
No word yet on citations for the crash.