# UNDF: UNDF-2026-000001009
--- a/src/simutrans/simhalt.cc
+++ b/src/simutrans/simhalt.cc
@@ -1222,6 +1222,10 @@
 sint32 haltestelle_t::rebuild_connections()
 {
 	// halts which either immediately precede or succeed self halt in serving schedules
 	static vector_tpl<halthandle_t> consecutive_halts[256];
+	// hash sets for O(1) dedup of consecutive halts (replaces append_unique
+	// linear scan which was O(S^2) per category where S = schedule entries)
+	static inthashtable_tpl<uint16, bool> consecutive_halts_seen[256];
 	// halts which either immediately precede or succeed self halt in currently processed schedule
 	static vector_tpl<halthandle_t> consecutive_halts_schedule[256];
+	static inthashtable_tpl<uint16, bool> consecutive_halts_schedule_seen[256];
 	// remember max number of consecutive halts for one schedule
 	uint8 max_consecutive_halts_schedule[256];
@@ -1234,6 +1238,8 @@
 	for(  uint8 i=0;  i<goods_manager_t::get_max_catg_index();  i++  ){
 		all_links[i].clear();
 		consecutive_halts[i].clear();
+		consecutive_halts_seen[i].clear();
 	}
 	old_sort_mode = 255; // might result in error in routing

@@ -1296,6 +1302,7 @@
 		for(uint8 const catg_index : *goods_catg_index) {
 			if(  is_enabled(catg_index)  ) {
 				supported_catg_index.append(catg_index);
 				previous_halt[catg_index] = self;
 				consecutive_halts_schedule[catg_index].clear();
+				consecutive_halts_schedule_seen[catg_index].clear();
 			}
 		}

@@ -1320,8 +1327,18 @@
 			if(  current_halt == self  ) {
 				// check for consecutive halts which precede self halt
 				for(uint8 const catg_index : supported_catg_index) {
 					if(  previous_halt[catg_index]!=self  ) {
-						consecutive_halts[catg_index].append_unique(previous_halt[catg_index]);
-						consecutive_halts_schedule[catg_index].append_unique(previous_halt[catg_index]);
+						uint16 halt_id = previous_halt[catg_index].get_id();
+						if(  !consecutive_halts_seen[catg_index].get(halt_id)  ) {
+							consecutive_halts_seen[catg_index].put(halt_id, true);
+							consecutive_halts[catg_index].append(previous_halt[catg_index]);
+						}
+						if(  !consecutive_halts_schedule_seen[catg_index].get(halt_id)  ) {
+							consecutive_halts_schedule_seen[catg_index].put(halt_id, true);
+							consecutive_halts_schedule[catg_index].append(previous_halt[catg_index]);
+						}
 						previous_halt[catg_index] = self;
 					}
 				}
@@ -1338,8 +1355,16 @@
 				if(  current_halt->is_enabled(catg_index)  ) {
 					// check for consecutive halts which succeed self halt
 					if(  previous_halt[catg_index] == self  ) {
-						consecutive_halts[catg_index].append_unique(current_halt);
-						consecutive_halts_schedule[catg_index].append_unique(current_halt);
+						uint16 halt_id = current_halt.get_id();
+						if(  !consecutive_halts_seen[catg_index].get(halt_id)  ) {
+							consecutive_halts_seen[catg_index].put(halt_id, true);
+							consecutive_halts[catg_index].append(current_halt);
+						}
+						if(  !consecutive_halts_schedule_seen[catg_index].get(halt_id)  ) {
+							consecutive_halts_schedule_seen[catg_index].put(halt_id, true);
+							consecutive_halts_schedule[catg_index].append(current_halt);
+						}
 					}
 					previous_halt[catg_index] = current_halt;