Abstract: A sleeping berth unit comprises at least two shape-retaining sub-modules shaped so that those sub-modules can interconnect in a sliding manner. The unit is mounted on the roof of a vehicle, at least one sub-module being fixed to the vehicle, leaving at least one sub-module free to slide back and forth. The unit is compressed into transit mode, or expanded into accommodation mode, with a single sliding action. The unit is accessed through a door at the end of at least one sub-module, via an extendable ladder. The ladder locates securely to the access door sub-module, and, if required, acts as a stabiliser for the unit. The sleeping berth unit access door sub-module(s) can be replaced with blanking module(s) to create a storage unit.