You're kidding, right? Aside from actively plotting the most inefficient course possible, this is about as inefficient as it gets. Aside from the fact that the driver can access the truck easily from both ends, the packages are arranged on shelves either side, so size doesn't really factor in to access.

Assuming a randomized distribution of small and large packages, a delivery route based on size would send the driver all over town and back again. No, the delivery routes are setup to be as efficient as possible—each package being delivered in an ordered designed to minimize driving time and distance as much as possible, regardless of package size.