Level 3 is in principle included in the ERTMS specifications, but only after the specifications became mature (Baseline 3) the railways started seriously to think about implementing Level 3. The general thinking about Level 3 takes place in Shift2Rail. They cover 4 different variants:
- Moving Block without trackside train detection
- Moving Block with trackside train detection
- Fixed Virtual Block without trackside train detection
- Fixed Virtual Block with trackside train detection
EUG is fully involved in this S2R work on Level 3, by organising the railway input from operational and engineering perspective.
Prior to the start of the S2R Level 3 work, and based on a Network Rail and ProRail initiative, EUG had developed the so called Hybrid Level 3 (HL3) concept. It is a detailed description of variant 4 of the S2R Level 3 work. This HL3 concept has been tested in the ENIF test facility, provided by Network Rail, in Hitchin UK. The tests have been successful. Some minor issues where detected, upon which the HL3 specifications were corrected, but the concept appeared to meet the expectations in a real live implementation. The HL3 concept is a trackside implementation which complements the ERTMS Baseline 3 specifications, i.e. it does not change these specifications. The HL3 concept allows to reduce the trackside train detection substantially compared to ETCS Level 2. The advantage of keeping a limited implementation of trackside train detection is that this mitigates the disadvantages of the "pure" Level 3. It allows for instance to run trains without an integrity monitoring function (albeit with lower performance) and it mitigates the potential problems with trains which are not connected to the RBC, either due to communication failure (unintential) or due to End of Mission (intentional).
The HL3 concept is publicly available and can be downloaded from this website.