Halton Region police say they got a call just after 3:30 a.m. from a couple who had pulled over onto the shoulder of Highway 401, just east of Highway 25.
The couple, from Milton, Ont., were heading to a nearby hospital for their baby's birth when they called for help.
Sgt. Ryan Snow responded to the call and minutes later — in the midst of heavy traffic and a -18 C wind chill — helped deliver a baby girl.
Police say the baby and her parents are all doing well and the mother and daughter were taken to Milton District Hospital by ambulance for precautionary reasons.
It's the second child for the couple.