Amazon.com has partnered with General Motors Co. and Volvo Cars to deliver packages to car trunks in 37 U.S. cities, as the e-commerce giant seeks new delivery methods for customers who may be wary of leaving packages outside or allowing couriers into their homes.

ATLANTA — A combination of better equipment, increasing governmental pressure and improving economics is aligning to make a case that alternative-power options can make practical sense to meet the trucking industry’s growing last-mile delivery needs, experts said.