The crash occurred at about 1:50 a.m. near Summit Avenue. Police say two Bergen County police cars had stopped on Route 46 because one of them was having a problem with his police radio.
The police car being driven by Officer Daniel Breslin was struck from behind by a Ford Fusion.
The impact left Breslin pinned inside his vehicle.
After being extricated, he was taken to Hackensack University Medical Center with a fractured skull, and also reportedly suffered broken ribs. Breslin, 39, is married with three children and has been with the county police force since 2010.
The driver of the other car got out and took off on foot, but the Lodi Police Department tracked him down in a backyard nearby on Christopher Court.
The driver, identified as 37-year old Michael Ettz of Lodi, suffered minor injuries. He was arrested and charged with DWI. Ettz is a mathematics teacher and athletics coach at Lodi High School.