This paper presents the fuel consumption reduction experienced by two heavy-duty trucks driving at close spacing. The trucks were coupled without any mechanical contact using an Electronic Tow Bar developed within the European project PROMOTE-CHAUFFEUR at DaimlerChrysler. The experiments were carried out on a level test track with constant velocities and with spacing between 6 and 16 m. As expected from other studies, both trucks experienced a considerable fuel consumption reduction compared to drives in isolation. At a velocity of 80km/h and a spacing of 10 m the measured fuel consumption reduction was of about 21 percent for the trail truck which had a total weight of 28 t. An extrapolation of the results for other vehicle weights is also presented. For the covering abstract see ITRD E108169.