diff --git a/connection_scan_algorithm/include/calculator.hpp b/connection_scan_algorithm/include/calculator.hpp
index 1c66a29..640862e 100644
--- a/connection_scan_algorithm/include/calculator.hpp
+++ b/connection_scan_algorithm/include/calculator.hpp
@@ -119,9 +119,10 @@ namespace TrRouting
     std::unordered_map<Node::uid_t, NodeTimeDistance> nodesEgress; // travel time/distance to reach destination;
 
     // Field used at the time of the query, mostly for alternatives, which deactivate some of the scenario trips. Typically, there are less disabled trips and enabled ones, so we keep only those
+    // Since the number of disabled trip is more commonly low, the map query is fast
     std::unordered_map<Trip::uid_t, bool> tripsDisabled;
     bool isTripDisabled(Trip::uid_t uid) const { return tripsDisabled.find(uid) != tripsDisabled.end(); }
-    std::unordered_map<Trip::uid_t, TripQueryData> tripsQueryOverlay; // Store addition trip info during a query processing
+    std::vector<TripQueryData> tripsQueryOverlay; // Store additionnal trip info during a query processing, indexed by Trip::uid
     // A subset of the connections that are used for the current query.
     std::shared_ptr<ConnectionSet> connectionSet;
 
diff --git a/connection_scan_algorithm/src/forward_calculation.cpp b/connection_scan_algorithm/src/forward_calculation.cpp
index 8e6d91e..2359352 100644
--- a/connection_scan_algorithm/src/forward_calculation.cpp
+++ b/connection_scan_algorithm/src/forward_calculation.cpp
@@ -47,7 +47,7 @@ namespace TrRouting
         const Trip & trip = (*connection).get().getTrip();
 
         // Cache the current query data overlay si we don't check the hashmap every time
-        auto & currentTripQueryOverlay = tripsQueryOverlay[trip.uid];
+        auto & currentTripQueryOverlay = tripsQueryOverlay.at(trip.uid);
 
         // enabled trips only here:
         if (!isTripDisabled(trip.uid))
@@ -237,7 +237,7 @@ namespace TrRouting
         const Trip & trip = (*connection).get().getTrip();
 
         // Cache the current query data overlay si we don't check the hashmap every time
-        auto & currentTripQueryOverlay = tripsQueryOverlay[trip.uid];
+        auto & currentTripQueryOverlay = tripsQueryOverlay.at(trip.uid);
 
         // enabled trips only here:
         if (!isTripDisabled(trip.uid))
diff --git a/connection_scan_algorithm/src/resets.cpp b/connection_scan_algorithm/src/resets.cpp
index c847137..02c3b52 100644
--- a/connection_scan_algorithm/src/resets.cpp
+++ b/connection_scan_algorithm/src/resets.cpp
@@ -34,7 +34,7 @@ namespace TrRouting
       egressFootpaths.clear();
       egressFootpaths.shrink_to_fit();
     }
-    tripsQueryOverlay.clear();
+    tripsQueryOverlay.assign(Trip::getMaxUid()+1, TripQueryData());
     forwardJourneysSteps.clear();
     reverseJourneysSteps.clear();
 
diff --git a/connection_scan_algorithm/src/reverse_calculation.cpp b/connection_scan_algorithm/src/reverse_calculation.cpp
index 960c1a6..be53d6f 100644
--- a/connection_scan_algorithm/src/reverse_calculation.cpp
+++ b/connection_scan_algorithm/src/reverse_calculation.cpp
@@ -53,7 +53,7 @@ namespace TrRouting
         const Trip & trip = (*connection).get().getTrip();
         
         // enabled trips only here:
-        auto & currentTripQueryOverlay = tripsQueryOverlay[trip.uid];
+        auto & currentTripQueryOverlay = tripsQueryOverlay.at(trip.uid);
         if (currentTripQueryOverlay.usable && !isTripDisabled(trip.uid))
         {
 
@@ -262,7 +262,7 @@ namespace TrRouting
         const Trip & trip = (*connection).get().getTrip();
 
         // enabled trips only here:
-        auto & currentTripQueryOverlay = tripsQueryOverlay[trip.uid];
+        auto & currentTripQueryOverlay = tripsQueryOverlay.at(trip.uid);
         // FIXME Determine with the new connection cache if a trip could be disabled in the all nodes path
         if ((currentTripQueryOverlay.usable) && !isTripDisabled(trip.uid))
         {
diff --git a/include/trip.hpp b/include/trip.hpp
index e6f551c..01ae34c 100644
--- a/include/trip.hpp
+++ b/include/trip.hpp
@@ -53,6 +53,8 @@ namespace TrRouting
     uid_t uid; //Local, temporary unique id, used to speed up lookups
 
     inline bool operator==(const Trip& other ) const { return uuid == other.uuid; }
+
+    static uid_t getMaxUid() { return global_uid; }
   private:
     //TODO, this could probably be an unsigned long, but current MAX_INT is good enough for our needs
     inline static uid_t global_uid = 0;