diff --git a/frontend/src/businessData.tsx b/frontend/src/businessData.tsx
index 4383022..c2e2388 100644
--- a/frontend/src/businessData.tsx
+++ b/frontend/src/businessData.tsx
@@ -61,7 +61,20 @@ export function BusinessDataProvider(props: { children: JSX.Element }) {
 	}
 
 	const addPassages = (passages: Passages): void => {
-		setStore('passages', passages);
+		const storePassages = store.passages;
+		for (const lineId of Object.keys(passages)) {
+			const newLinePassages = passages[lineId];
+			const linePassages = storePassages[lineId];
+			if (linePassages === undefined) {
+				setStore('passages', lineId, newLinePassages);
+			}
+			else {
+				for (const destination of Object.keys(newLinePassages)) {
+					const newLinePassagesDestination = newLinePassages[destination];
+					setStore('passages', lineId, destination, newLinePassagesDestination);
+				}
+			}
+		}
 	}
 
 	const clearPassages = (): void => {