# UNDF: UNDF-2026-000001007
--- a/src/simutrans/simhalt.cc
+++ b/src/simutrans/simhalt.cc
@@ -1374,13 +1374,22 @@

 void haltestelle_t::rebuild_linked_connections()
 {
-	vector_tpl<halthandle_t> all; // all halts connected to this halt
-	for(  uint8 i=0;  i<goods_manager_t::get_max_catg_index();  i++  ){
+	// Collect unique connected halts using a hash set for O(1) membership test.
+	// Previously used append_unique (linear scan) inside a double loop over
+	// categories x connections, giving O(C * H^2) where H = connected halts.
+	// With the hash set this becomes O(C * H).
+	inthashtable_tpl<uint16, bool> seen;
+	vector_tpl<halthandle_t> all;
+	for(  uint8 i=0;  i<goods_manager_t::get_max_catg_index();  i++  ) {
 		vector_tpl<connection_t>& connections = all_links[i].connections;

 		for(connection_t &c : connections) {
-			all.append_unique( c.halt );
+			if(  c.halt.is_bound()  ) {
+				uint16 halt_id = c.halt.get_id();
+				if(  !seen.get(halt_id)  ) {
+					seen.put(halt_id, true);
+					all.append(c.halt);
+				}
+			}
 		}
 	}
 	for(halthandle_t h : all) {