Truck emissions are a huge contributor to poor air quality, but all electric seems unlikely for heavy trucks for a long time. Even so, electric assist could improve performance while reducing fuel consumption. Heavy trucks waste a lot of fuel climbing hills, braking down hills, and in stop and go traffic. Even large Diesel engines burn a lot of fuel pulling a load to build momentum from a dead stop, and current engine braking and air brakes waste vast amounts of energy during deceleration, especially down hills. In addition, driver cab power needs during down time, when the truck is stopped, unnecessarily burns fuel either by truck engine idling or by an auxiliary motor (Apu).
I'd like to see Tesla Engineers working with truck makers, or maybe with a transaxle make like Meritor, to develop a regenerative braking system and electric motor on the drive axle. When the driver flips on the jake brake, a computer modulates a combination of engine braking and regenerative braking for optimal electrical charge and deceleration.. When the driver steps on the brake, air brakes are assisted by regenerative braking, computer controlled to avoid loss of control even under icy conditions. From a dead stop at a traffic light, for instance, electric motor assistance could improve initial acceleration, and during a hill climb, stored battery charge could boost power by, say, 50 HP.
Currently, DOT regulated drivers are required to take 10 hours rest for every 14 hrs duty, downtime that requires surprising power for sleeper cab habitability and entertainment. Engine idling, which consumes about 1/2 gallon diesel per hour is illegal in CA but remains very routine for many drivers because cab habitability trumps the law during hot and cold weather. Diesel burning APU, small one cylinder auxiliary engines, are much more fuel efficient, but are noisy and really don't provide adequate electrical power to maintain wet cell batteries drained by the array of electrical gadgets, A/C, and kitchen appliances drivers often power in their condo sleeper cabs. None of the current electrical standby systems for trucks cabs provide sufficient electrical power IMHO.
A substantial Toyota Prius sized battery that can provide 10 hours (ideally a full weekend for stranded drivers) AND a source of electrical power for a Tesla sized transaxle mounted motor would be great. Most if not all of the charge for this battery could come from what is now discarded heat on the brake shoes, so service life of drums and shoes would be extended while cab habitation is improved. A combination regenerative brake and electric motor could also reduce fuel consumption because the main diesel motor could be slightly smaller in HP, yet performance would be improved on hills and in heavy traffic.
Eventually, of course, the diesel burning motor would be replaced by fuel cell technology or some other high energy zero emission power source. Next time you drive your 2,000 pound Tesla on the freeway, consider the number of out-of-state 80,000 pound vehicles around you pumping emissions into the air. This is an awesome and growing contribution to global climate change.