Better yet would be deliveries every other day; not including Sundays. Roughly 1/2 the number of vehicles would be needed along with 1/2 the maintenance and fuel costs.
That’s what I would do, cut back on some of the rural deliveries (Say within a mile radius) and cut postal service to 4 days per week.
Why is no one talking about urban door to door delivery? How much does that cost?
I lived in a trailer park some years ago and had a block of PO boxes at the end of the street that worked fine.