Highway 101 was a major thoroughfare for vehicles running through California on Earth. During the 20th century, it was known for being clogged at certain times of the day in the city of Los Angeles.
In 1996, Henry Starling instructed his limousine driver H. Dunbar to avoid Highway 101 after picking up Rain Robinson at Metro Plaza, stating that the traffic would be a "nightmare". (VOY: "Future's End, Part II")