Commuter

Puzzle

A commuter rides the train to and from work each day. Her husband meets her at the train station and drives her home. One day the commuter leaves work early, catches a different train and arrives at the station one hour ahead of schedule. It being a nice day, she decides to walk toward home. Somewhere along the way she meets her husband, driving from home to pick her up at the usual time. She gets in the car and they drive back, arriving 20 minutes earlier than normal. How long was the commuter walking?