--- a/src/ai/api/ai_bridge.cpp	Tue Apr 15 22:18:11 2008 +0000
+++ b/src/ai/api/ai_bridge.cpp	Tue Apr 15 22:29:00 2008 +0000
@@ -58,39 +58,39 @@
 	return bridge_name;
 }
 
-/* static */ uint32 AIBridge::GetMaxSpeed(BridgeID bridge_id)
+/* static */ int32 AIBridge::GetMaxSpeed(BridgeID bridge_id)
 {
-	if (!IsValidBridge(bridge_id)) return 0;
+	if (!IsValidBridge(bridge_id)) return -1;
 
 	return ::GetBridgeSpec(bridge_id)->speed;
 }
 
-/* static */ uint32 AIBridge::GetPrice(BridgeID bridge_id, uint length)
+/* static */ int32 AIBridge::GetPrice(BridgeID bridge_id, uint length)
 {
-	if (!IsValidBridge(bridge_id)) return 0;
+	if (!IsValidBridge(bridge_id)) return -1;
 
 	return length * _price.build_bridge * ::GetBridgeSpec(bridge_id)->price >> 8;
 }
 
-/* static */ uint32 AIBridge::GetMaxLength(BridgeID bridge_id)
+/* static */ int32 AIBridge::GetMaxLength(BridgeID bridge_id)
 {
-	if (!IsValidBridge(bridge_id)) return 0;
+	if (!IsValidBridge(bridge_id)) return -1;
 
 	uint max = ::GetBridgeSpec(bridge_id)->max_length;
 	if (max >= 16 && _patches.longbridges) max = 100;
 	return max + 2;
 }
 
-/* static */ uint32 AIBridge::GetMinLength(BridgeID bridge_id)
+/* static */ int32 AIBridge::GetMinLength(BridgeID bridge_id)
 {
-	if (!IsValidBridge(bridge_id)) return 0;
+	if (!IsValidBridge(bridge_id)) return -1;
 
 	return ::GetBridgeSpec(bridge_id)->min_length + 2;
 }
 
 /* static */ int32 AIBridge::GetYearAvailable(BridgeID bridge_id)
 {
-	if (!IsValidBridge(bridge_id)) return 0;
+	if (!IsValidBridge(bridge_id)) return -1;
 
 	return ::GetBridgeSpec(bridge_id)->avail_year;
 }