# ETCS

European Train Control System

## Context

The onboard computer of ETCS-enabled trains has to compute a number of position / speed curves. Here is how it works:

- below all the curves, the speed indicator is white
- above the indication curve, the speed indicator is yellow
- above the permitted curve, the speed indicator is orange
- above the warning curve, an alarm rings
- above the intervention curves, an emergency break intervention is triggered

## Inputs

In order to compute any of these curves, a number of things are needed:

- target data (the destination of the braking curve, which can be EOA and SvL or LOA and MRSP)
- train data
- infrastructure data
- infrastructure manager constants
- standardized constants

### Train

- max speed
- length
- rotating mass
`T_traction_cutoff`

: the time it take to cut off traction- braking model, either lambda or gamma:
- lambda (braking weight/mass)
- gamma (contant deceleration at a given speed)

- correction factors (k_dry and k_wet for gamma braking) for braking curves

### Infrastructure

- corrected gradients (it incorporates curvature)
- odometry balises location

## Processes

### Braking coefficients:

`A_brake_emergency`

is the expected emergency braking capability, without safety margins`A_brake_safe`

is the emergency braking coefficient,**with**safety margins`A_brake_service`

is the expected service braking capability, without safety margins

### Speed / distance targets

`EOA`

end of movement authority: the location until which the train is allowed to move`SvL`

supervized location: the protected location

### Curves

`SBD`

supervised braking deceleration: intermediary result computed from`EOA`

and`A_brake_service`

`EBD`

emergency braking deceleration: intermediary result computed from`SvL`

and`A_brake_safe`

All the curves below are cut below a given release speed:

`EBI`

(emergency break intervention) computed from`EBD`

, shifted in position and space given rolling stock metadata`SBI1`

computed from`SBD`

, shifted in**time**with`Tbs1`

`SBI2`

computed from`SBD`

, shifted in**time**with`Tbs2`

`FLOI`

(also called`SBI`

, the intervention curve) the minimum of`SBI1`

and`SBI2`

`WARNING`

(warning curve) computed as a shift of`FLOI`

by`Twarning`

`PS`

(permitted speed curve): shift of`WARNING`

by time`Tdriver`

`INDICATION`

is a shift of`PS`

by time`Tindication`