The mainstream of electrification is currently for passenger cars and buses, but so far not so much trucks, while trucks are major fuel guzzlers.
According to the U.S. DOE’s Office of Energy Efficiency & Renewable Energy, in 2017 medium- and heavy-duty trucks accounted only for 4% of the total vehicle fleet in the U.S.
However, they traveled 9% of the total miles (mileage is usually two times higher than average) and consumed 26% of fuel, which translates to a very high corresponding share in emission.
See also
"Trucks in the medium/heavy truck category include tractor trailers, also known as combination trucks, and single-unit trucks. In the most recent year for which data are available, combination trucks made up only 1% of the truck population but were responsible for 6% of all vehicle miles traveled (VMT) and 17% of vehicle fuel use. Single-unit trucks were 3% of the truck population and 3% of VMT, while making up 9% of vehicle fuel use."
Knowing how much emissions comes from trucks, electrification seems one of the most urgent and reasonable goals.
Source: U.S. Department of Transportation, Federal Highway Administration, Highway Statistics 2017, Washington, DC, March 2019, Table VM-1.
Source: energy.gov