Rather than converting trucks themselves from diesel to electric, what if we put solar panels, electric motors and regenerative brakes into the trailer units?

https://spectrum.ieee.org/self-powered-trailers-freight-decarbonization

'Trailer Dynamics, an Aachen-based company, has conducted field tests with BMW Logistics, DB Schenker, Duvenbeck, and Volkswagen Konzernlogistik, reporting average fuel savings of around 40 percent for diesel tractor combinations ...'