The roll-out of ERTMS requires rail vehicles to be equipped with an intelligent ERTMS onboard computer (‘EVC’). However, EVC installation is not always feasible for unique (historic) rail vehicles or small vehicle series, because they usually require special solutions, and ERTMS suppliers have little appetite for such small-scale special
projects. Concurrently, small railway operators are not equipped for managing expensive contracts with ERTMS suppliers.

If no ERTMS solution is developed for such vehicles and their operators, they will be expelled from the network. TU Delft proposes the ERTMS-E concept as a solution. ERTMS-E works by dividing the EVC functionality across simple onboard electronics, with a wayside server running the EVC software. The onboard and wayside hardware are interconnected via wireless communications (e.g., FRMCS). This approach moves the intelligent software and hardware from the vehicles to the wayside, reducing the amount of proprietary equipment required for vehicle retrofitting. The simple onboard electronics and software could be bought cost-effectively by operators to install and maintain  themselves. The wayside server and associated software could be maintained and (TSI-)updated for a large group of operators / vehicles at the same time, leading to a cost-effective solution. ERTMS-E is compatible with ERTMS.