Semi-autonomous transportation systems are an intermediate step towards full automation of transportation systems. They use and benefit from the technological advances brought by automation while being already implementable at larger scale under the current regulations and within the existing urban environment.

In this paper, we present a new type of semi-autonomous transportation system referred to as Multi-Layered Personal Transit System (MuLPeTS). It consists of convoys composed of one human-driven lead vehicle guiding several autonomous small capacity trailers in which the passengers travel. These trailers can detach from a convoy and travel autonomously in a protected environment before attaching later to another convoy. The interest of this transportation concept is threefold: (i) this assembly of vehicles is able and allowed to move in mixed-traffic conditions whereas fully autonomous driving is still largely restricted; (ii) a trailer can travel autonomously in the vicinity of stations to pick-up and drop-off passengers while the convoy it was previously part of continues its route without further delay; and (iii) passengers complete their entire journey on board a single trailer, that is they avoid the need to transfer. We analyze how this new type of transportation system relates to existing alternatives and propose an operational concept for it, in which we account for passenger assignment, lead vehicle routes and trailer movements, including empty trailer relocation. We extensively test this concept within a purpose-built simulation environment to evaluate the performance of this kind of system based on real-world data instances. The results highlight the most promising operational policies and characterize favorable system configurations.