It's been almost 35 years since the USPS launched a new template for their mail trucks and, to say the least, they need an overhaul.
With no air conditioning, lack of insulation, and some older vehicles being a fire hazard, they certainly do not seem suited for the "neither snow nor rain nor heat" form of dedication that the Postal Service is known for.
AND there's reportedly still 140,000 of the original vehicles from 1985 (!!!) in operation.