SUBSET-040 — Dimensioning and Engineering rules

Scope

The ERTMS/ETCS specification setting the dimensioning and engineering rules that translate the functional and safety subsets into an installable trackside and onboard system: parameter ranges, sizing rules for balise groups and RBC/radio coverage, and the engineering constraints a signalling designer must respect for the system to behave as the functional specifications assume.

SUBSET-040 is the bridge between ETCS's functional specifications (what the system must do) and an actual engineering design (how a specific line gets fitted): it sets dimensioning rules and value ranges for system parameters — balise-group spacing and telegram sizing, odometry accuracy budgets, radio coverage and handover margins, national-values ranges — and the engineering constraints that keep a real installation inside the assumptions the ETCS functional subsets (national values, braking curves, movement-authority logic) were verified against. Where SUBSET-026 defines what the system computes, SUBSET-040 defines the engineering envelope within which that computation is valid. It is one of the mandatory specifications listed in Annex A (Table A2) of the CCS TSI, referenced there at v4.0.0 (ETCS Baseline 4) alongside SUBSET-034, -035, -038 and -114, and so is binding on any new ETCS trackside or onboard engineering design under Regulation (EU) 2023/1695. Signalling engineering firms, infrastructure managers designing ETCS fitment for a line, and onboard/trackside suppliers validating that their equipment's operating envelope matches a given installation's engineering parameters are its principal users.