Driver management and coaching is a popular and effective fuel-saver. These programs optimize shift patterns, manage and/or reduce average vehicle speed, and use telematics to optimize routes. Like automatic manual transmissions (which are not mutually exclusive), these changes run the engine at or near its optimal point as much as possible.
Since aerodynamic drag is about two-thirds of a typical heavy truck’s over-the-road tractive load, and the energy needed to overcome it rises as the cube of speed, each mph reduction in the range 60–65 mph improves fuel economy by about 0.4–0.5%. Taken together, driver training and feedback, instantaneous mpg notification, and reduced average speed have been shown to increase heavy truck fuel efficiency by 6%.
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Bockholt, Wendy, and Matthew Kromer. 2009. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. TIAX LLC. link