Here's the basic Type IV procedure. Two tractor- trailer combinations are dispatched together. And, during the one hour warm-up period, the drivers practice speed management using visual and voice contact. The right-side tank will be filled from the same pump, to assure equal heat content. The fuel is brought up to a predetermined point in each tank very carefully, and the temperature is taken with a remote-reading, digital thermometer from a point near the center of the tank.
Care is taken to assure that engine-on time and distances moved within the truck stop are equal.
Both drivers leave the fuel station together. The lead driver establishes and maintains the test speed while the following driver establishes and maintains a 15 to 45 second gap between the two vehicles. The drivers swap tractors but stay with the trailers they pulled during the first half of the run. This eliminates any effect that drivers or trailers might have on the test results. When the trucks leave the midpoint equipment-switch facility, the driver who led the first half of the test run must lead during the second half.