diff --git a/backend/backend/idfm_interface/idfm_interface.py b/backend/backend/idfm_interface/idfm_interface.py
index b6bf4b7..7bcc734 100644
--- a/backend/backend/idfm_interface/idfm_interface.py
+++ b/backend/backend/idfm_interface/idfm_interface.py
@@ -31,6 +31,10 @@ class IdfmInterface:
     async def startup(self) -> None:
         ...
 
+    @staticmethod
+    def _format_line_id(line_id: str) -> int:
+        return int(line_id[1:] if line_id[0] == "C" else line_id)
+
     async def render_line_picto(self, line: Line) -> tuple[None | str, None | str]:
         line_picto_path = line_picto_format = None
         target = f"/tmp/{line.id}_repr"
@@ -81,7 +85,6 @@ class IdfmInterface:
 
         if (stop := await Stop.get_by_id(stop_id)) is not None:
             expected_stop_ids = {stop.id}
-
         elif (stop_area := await StopArea.get_by_id(stop_id)) is not None:
             expected_stop_ids = {stop.id for stop in stop_area.stops}
         else:
@@ -105,7 +108,8 @@ class IdfmInterface:
                         if (
                             dst_names := journey.DestinationName
                         ) and monitored_stop_id in expected_stop_ids:
-                            line_id = journey.LineRef.value.split(":")[-2]
+                            raw_line_id = journey.LineRef.value.split(":")[-2]
+                            line_id = IdfmInterface._format_line_id(raw_line_id)
                             destinations[line_id].add(dst_names[0].value)
 
         return destinations
diff --git a/backend/backend/schemas/line.py b/backend/backend/schemas/line.py
index 01feeed..69f29bc 100644
--- a/backend/backend/schemas/line.py
+++ b/backend/backend/schemas/line.py
@@ -53,8 +53,8 @@ class Line(BaseModel):
     transportMode: TransportMode
     backColorHexa: str
     foreColorHexa: str
-    operatorId: str
+    operatorId: int
     accessibility: IdfmState
     visualSignsAvailable: IdfmState
     audibleSignsAvailable: IdfmState
-    stopIds: list[str]
+    stopIds: list[int]
diff --git a/backend/backend/schemas/stop.py b/backend/backend/schemas/stop.py
index 2bd6f6e..78581ac 100644
--- a/backend/backend/schemas/stop.py
+++ b/backend/backend/schemas/stop.py
@@ -9,7 +9,7 @@ class Stop(BaseModel):
     town: str
     epsg3857_x: float
     epsg3857_y: float
-    lines: list[str]
+    lines: list[int]
 
 
 class StopArea(BaseModel):
@@ -17,7 +17,7 @@ class StopArea(BaseModel):
     name: str
     town: str
     type: StopAreaType
-    lines: list[str]  # SNCF lines are linked to stop areas and not stops.
+    lines: list[int]  # SNCF lines are linked to stop areas and not stops.
     stops: list[Stop]
 
 
diff --git a/frontend/src/types.tsx b/frontend/src/types.tsx
index dd2da16..63d68d9 100644
--- a/frontend/src/types.tsx
+++ b/frontend/src/types.tsx
@@ -8,7 +8,7 @@ export enum TrafficStatus {
 
 export class Passage {
 	line: number;
-	operator: string;
+	operator: number;
 	destinations: string[];
 	atStop: boolean;
 	aimedArrivalTs: number;
@@ -19,7 +19,7 @@ export class Passage {
 	arrivalStatus: string;
 	departStatus: string;
 
-	constructor(line: number, operator: string, destinations: string[], atStop: boolean, aimedArrivalTs: number,
+	constructor(line: number, operator: number, destinations: string[], atStop: boolean, aimedArrivalTs: number,
 		expectedArrivalTs: number, arrivalPlatformName: string, aimedDepartTs: number, expectedDepartTs: number,
 		arrivalStatus: string, departStatus: string) {
 		this.line = line;
@@ -45,9 +45,9 @@ export class Stop {
 	epsg3857_x: number;
 	epsg3857_y: number;
 	stops: Stop[];
-	lines: string[];
+	lines: number[];
 
-	constructor(id: number, name: string, town: string, epsg3857_x: number, epsg3857_y: number, stops: Stop[], lines: string[]) {
+	constructor(id: number, name: string, town: string, epsg3857_x: number, epsg3857_y: number, stops: Stop[], lines: number[]) {
 		this.id = id;
 		this.name = name;
 		this.town = town;
@@ -82,7 +82,7 @@ export class StopShape {
 export type StopShapes = Record<number, StopShape>;
 
 export class Line {
-	id: string;
+	id: number;
 	shortName: string;
 	name: string;
 	status: string; // TODO: Use an enum
@@ -95,7 +95,7 @@ export class Line {
 	audibleSignsAvailable: string; // TODO: Use an enum
 	stopIds: number[];
 
-	constructor(id: string, shortName: string, name: string, status: string, transportMode: string, backColorHexa: string,
+	constructor(id: number, shortName: string, name: string, status: string, transportMode: string, backColorHexa: string,
 		foreColorHexa: string, operatorId: number, accessibility: boolean, visualSignsAvailable: string,
 		audibleSignsAvailable: string, stopIds: number[]) {
 		this.id = id;