The fuel consumption of two tandem trucks is recorded for truck spacings of 3, 4, 6, 8, and 10 meters. The trucks are linked by means of an electronic control system, and are operated on an unused runway at Crows Landing, California. Fuel consumption data is averaged while traveling in both directions over the same central strip of runway to cancel the effect of runway slope and to partially cancel the effect of wind. The average fuel consumption saving to be achieved by tandem operation varies from about 11% at 3-4 meters spacing to about 8% at 8-10 meters spacing.