Each country has their own circumstances to deal with. This design would not make sense in Europe where a lot of the last mile delivery was done by mail carriers on foot or bicycles. However it does boost efficiency considerably in the USA's vast expanse of suburbia. FWIW, mail trucks in Canada also have with right hand drive and low floor so the driver could reach into mailboxes without having to leave their seat.

My local postal service used to make delivery on bicycles but they have gradually introduced golf-cart like miniature EVs. This allow each run to cover a much larger area but probably would not for the most of US because their mail routes are too long.

> However it does boost efficiency considerably in the USA's vast expanse of suburbia.

Also it sounds like the new trucks have pretty stringent visibility requirements, which would help avoid running over playing children in a suburban setting. I can see that as a pretty serious risk for the USPS, given how frequently they stop for a few minutes. An off-the-shelf van without the unusually shaped front probably has more blind spots a kid could sneak into.

Quite a few national postal services use custom or semi-custom vehicles, e.g. Deutsche Post. For those that use more "off the shelf" vehicles they are probably still custom orders specifying an exact feature set. But at the end of the day, it just becomes a matter of cost/benefit. The USPS is enormous, and that large scale makes it financially viable for them to purchase a custom vehicle since the quantities are so great. This allows them to get exactly what they want which gains some operating efficiency.

Oshkosh is also a very well established manufacturer of vehicles for the government and holds substantial military contracts for custom vehicles such as the highly recognizable HEMTT. So the Oshkosh purchase is fairly low-risk in that Oshkosh has a proven track record of delivering vehicles for government fleets.

UPS and FedEx also make use of largely custom vehicles. They are based on off-the-shelf step vans, but to a large extent OTS step vans no longer exist in the US and nearly all of them you see are contract designs for fleets. There's a bit of a cyclical relationship here as the modern step van is basically defined by UPS and FedEx, which purchase their trucks custom to specification from body-makers like Utilimaster and formerly Grumman-Olson. Grumman popping up here again is not coincidental - the USPS and UPS formerly got their custom trucks from the same manufacturer, but Grumman-Olson is no longer nearly as important of a player as it once was.

The short answer: USPS is contracting for at least 50,000 vehicles. When you buy 50,000 of just about anything you gain a lot of leverage to customize.

Most countries don't really have US-style mailboxes either.

And yet.....everyone manages. Houses in rural areas have mailboxes outside of the property, sure they are not the iconic american half-pipe shape, but properties all over the world have mailboxes too.

Right, everyone manages with what we have now so why change anything? I mean who cares if increased visibility reduces the number of pedestrian collisions, who cares if seat designs reduce the number of back injuries. The world is good enough as it is.

At scale it makes sense to have control of part supplies and have consistent service processes. UPS and to a lesser extent FedEx also use custom bodies.