I actually think that if handled correctly by Royal Mail (Yes I Know their track record), taking into account local conditions, work load, parking restrictions, human interaction etc..... . They could actually be good for the Posties:
Drawbacks or issues that need sorting
Will you get on with the person you are teamed up with.
Splitting workload between Driver and non driver
Prep work
Vehicle checks
Overnight responsibility
Size of Loops
Bodily needs
Work Load and balance
Cutting off procedure (single and team)
Wilful delay responsibility
Driver responsibility when there are 2 drivers.
But there are benefits.
No guessing on weather and either getting wet through or too warm because you guessed wrong.
Somewhere to have a break or shelter in really bad weather
A refuge or means of escape from dogs/irate customer.
Somewhere to store extra clothing, food, warm/cold drink and snacks
Better service for customers in that no longer waiting for 48 hours to collect.
No waiting on bags if your at end of drivers routes.
Packet deliveries will have more knowledge of customers and their idiosyncrasies.
Somewhere warm when its really cold.
As with most things in life there are drawback and benefits to this method of delivery -
Ducks head and waits for replies.