Tandem dream meaning is explained below using 3 different sources. Each interpretation is shown with its source.

Interpretation 1 — Stephen Girard

To dream that you are driving tandem, denotes that you will be prosperous in business, and in the marriage state.
Source: The Mystic Dream Book Author: Stephen Girard

Interpretation 2 — Raymond Buckland

To dream of a tandem bicycle means you will be going into partnership, either in business or by getting married.
Source: Gypsy Dream Dictionary Author: Raymond Buckland

Interpretation 3 — Internet Archive - Anonymous

To dream of driving horses in this manner signifies two lovers who will cause you difficulty through jealousy.
Source: Mystic Dream Book Author: Internet Archive - Anonymous