diff --git a/src/timetable_cmd.cpp b/src/timetable_cmd.cpp
index 1aefc842d5..cab96aa36a 100644
--- a/src/timetable_cmd.cpp
+++ b/src/timetable_cmd.cpp
@@ -911,29 +911,36 @@ void UpdateVehicleTimetable(Vehicle *v, bool travelling)
 		int32 new_time;
 		if (travelling) {
 			new_time = time_taken;
+			if (new_time > (int32)timetabled * 4) {
+				/* Possible jam, clear time and restart timetable for all vehicles.
+				 * Otherwise we risk trains blocking 1-lane stations for long times. */
+				ChangeTimetable(v, v->cur_timetable_order_index, 0, travel_field ? MTF_TRAVEL_TIME : MTF_WAIT_TIME, true);
+				for (Vehicle *v2 = v->FirstShared(); v2 != nullptr; v2 = v2->NextShared()) {
+					v2->ClearSeparation();
+					ClrBit(v2->vehicle_flags, VF_TIMETABLE_STARTED);
+					SetWindowDirty(WC_VEHICLE_TIMETABLE, v2->index);
+				}
+				return;
+			} else if (new_time >= (int32)timetabled / 2) {
+				/* Compute running average, with sign conversion to avoid negative overflow.
+				 * This is biased to favour negative adjustments */
+				if (new_time < (int32)timetabled) {
+					new_time = ((int32)timetabled * 3 + new_time * 2 + 2) / 5;
+				} else {
+					new_time = ((int32)timetabled * 9 + new_time + 5) / 10;
+				}
+			} else {
+				/* new time is less than half the old time, set value directly */
+			}
 		} else {
 			new_time = time_loading;
-		}
-
-		if (new_time > (int32)timetabled * 4 && travelling) {
-			/* Possible jam, clear time and restart timetable for all vehicles.
-			 * Otherwise we risk trains blocking 1-lane stations for long times. */
-			ChangeTimetable(v, v->cur_timetable_order_index, 0, travel_field ? MTF_TRAVEL_TIME : MTF_WAIT_TIME, true);
-			for (Vehicle *v2 = v->FirstShared(); v2 != nullptr; v2 = v2->NextShared()) {
-				v2->ClearSeparation();
-				ClrBit(v2->vehicle_flags, VF_TIMETABLE_STARTED);
-				SetWindowDirty(WC_VEHICLE_TIMETABLE, v2->index);
-			}
-			return;
-		} else if (new_time >= (int32)timetabled / 2) {
-			/* Compute running average, with sign conversion to avoid negative overflow. */
-			if (new_time < (int32)timetabled) {
+			/* Compute running average, with sign conversion to avoid negative overflow.
+			 * This is biased to favour positive adjustments */
+			if (new_time > (int32)timetabled) {
 				new_time = ((int32)timetabled * 3 + new_time * 2 + 2) / 5;
 			} else {
 				new_time = ((int32)timetabled * 9 + new_time + 5) / 10;
 			}
-		} else {
-			/* new time is less than hald old time, set value directly */
 		}
 
 		if (new_time < 1) new_time = 1;