diff --git a/core/src/main/kotlin/fr/sncf/osrd/ertms/etcs/ETCSBrakingSimulator.kt b/core/src/main/kotlin/fr/sncf/osrd/ertms/etcs/ETCSBrakingSimulator.kt
new file mode 100644
index 00000000000..a6b2047dc8a
--- /dev/null
+++ b/core/src/main/kotlin/fr/sncf/osrd/ertms/etcs/ETCSBrakingSimulator.kt
@@ -0,0 +1,51 @@
+package fr.sncf.osrd.ertms.etcs
+
+import fr.sncf.osrd.envelope.Envelope
+import fr.sncf.osrd.sim_infra.api.Path
+import fr.sncf.osrd.sim_infra.api.PathProperties
+import fr.sncf.osrd.train.RollingStock
+import fr.sncf.osrd.utils.units.Offset
+
+interface ETCSBrakingSimulator {
+    val trainPath: PathProperties
+    val rollingStock: RollingStock
+    val timeStep: Double
+
+    /**
+     * Compute the ETCS braking envelope from the MRSP: for each decreasing speed transition,
+     * compute the corresponding ETCS braking curve.
+     */
+    fun getETCSBrakingEnvelopeFromMrsp(mrsp: Envelope)
+
+    /**
+     * Compute the ETCS braking envelope from target: compute the corresponding ETCS braking curve
+     * decreasing from rolling stock max speed and ending at target offset/speed-wise.
+     */
+    fun getETCSBrakingEnvelopeFromTarget(target: Target)
+}
+
+data class Target(
+    val offset: Offset<Path>,
+    val speed: Double,
+    val type: TargetType = if (speed != 0.0) TargetType.SLOWDOWN else TargetType.STOP
+)
+
+enum class TargetType {
+    SLOWDOWN,
+    STOP
+}
+
+class ETCSBrakingSimulatorImpl(
+    override val trainPath: PathProperties,
+    override val rollingStock: RollingStock,
+    override val timeStep: Double
+) : ETCSBrakingSimulator {
+
+    override fun getETCSBrakingEnvelopeFromMrsp(mrsp: Envelope) {
+        TODO("Not yet implemented")
+    }
+
+    override fun getETCSBrakingEnvelopeFromTarget(target: Target) {
+        TODO("Not yet implemented")
+    }
+}