As an aside, I am surprised that HGV trucks don't utilise the diesel-electric method. One whould have thought such a system would save shedloads of fuel,
Apologies for the thread drift, but the easiest way to get better fuel economy from trucks is to modify the drivers habits, such that they don't go rushing up to junctions and then slam on their brakes, as if fuel was free (well, it is, to them).