Isopods

Isopods are the long, centipede-like crustaceans engineered by Grand Cluster City to serve as public transit. Cold and efficient, they are as timely as any transit system back on earth. To achieve this, they were engineered to never need food or sleep, and stop for nothing until reaching one of the designated busports of the city. Because of this, it's common for Isopods to work themselves to death, which the city's engineers have also accounted for. To keep the rail system free of Isopod corpses, the city engineers simply had hominids dig deep pits under the Isopod rail system that an Isopod--and potentially its passengers--can simply fall into when it enevitably dies and runs off the rails.