Embodiments provide shelves, bracket systems, automated picker robots, totes, and other features that may be used with delivery vehicle configurations that have automated cargo areas. A delivery vehicle may include a picking robot that selectively retrieves packages for delivery without requiring substantial human intervention for locating those packages. The cargo area of the delivery vehicle may further comprise a plurality of customizable shelving units that generate custom-sized shelves for packages. The shelves may include a plurality of individually movable shelf brackets having retaining members that pivot between an extended and retracted position to hold the package in place and to enable the picking robot to retrieve the package from the shelf. Another embodiment provides for a tote having a drive mechanism to hold letters so that a letter may be automatically retrieved from the cargo area and provided at a delivery location.