Autotrén is a system of Group Rapid Transportation (""GRT"") technology for rapid and sustainable mobility in saturated corridors and medium-sized cities.

It consists of a fleet of ultra-light, electric and autonomous trains (without human driver), which are formed from 1 to 4 wagons, for up to 24 passengers. Its roads are exclusive, elevated or underground lanes, whose width is half the width of conventional bus or train lanes. The passenger stations are always located in parallel lanes.

Vehicles circulate in the main lanes at 4 second intervals, stopping only at those stations where they will go up or down, operating in a similar way to an intelligent elevator where all routes are express and scheduled on demand.

TÜV Rheinland evaluated the documentation required for the Safety Demonstration of the company MODUTRAM (Autotrén Transport System), in particular to the Train Control System based on CBTC communication. The aim of TÜV Rheinland was for the customer to know the requirements and safety functions and their correct management, as well as the level of compliance of a system with respect to railway safety regulations.