diff --git a/application/src/ext/java/org/opentripplanner/ext/flex/FlexIndex.java b/application/src/ext/java/org/opentripplanner/ext/flex/FlexIndex.java
index 86d9766178f..8097bd05c6e 100644
--- a/application/src/ext/java/org/opentripplanner/ext/flex/FlexIndex.java
+++ b/application/src/ext/java/org/opentripplanner/ext/flex/FlexIndex.java
@@ -5,7 +5,6 @@
 import com.google.common.collect.Multimap;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.List;
 import java.util.Map;
 import org.opentripplanner.ext.flex.trip.FlexTrip;
 import org.opentripplanner.model.PathTransfer;
diff --git a/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/RaptorTransferIndex.java b/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/RaptorTransferIndex.java
index 941e1296838..8676e863911 100644
--- a/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/RaptorTransferIndex.java
+++ b/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/RaptorTransferIndex.java
@@ -33,7 +33,6 @@ public static RaptorTransferIndex create(
     StreetMode mode = request.mode();
 
     for (int i = 0; i < transfersByStopIndex.size(); i++) {
-      forwardTransfers.add(new ArrayList<>());
       reversedTransfers.add(new ArrayList<>());
     }
 
@@ -43,14 +42,14 @@ public static RaptorTransferIndex create(
       var transfers = transfersByStopIndex
         .get(fromStop)
         .stream()
-        .filter(transfer -> transfer.getModes().contains(mode))
+        .filter(transfer -> transfer.allowsMode(mode))
         .flatMap(s -> s.asRaptorTransfer(request).stream())
         .collect(
           toMap(RaptorTransfer::stop, Function.identity(), (a, b) -> a.c1() < b.c1() ? a : b)
         )
         .values();
 
-      forwardTransfers.get(fromStop).addAll(transfers);
+      forwardTransfers.add(new ArrayList<>(transfers));
 
       for (RaptorTransfer forwardTransfer : transfers) {
         reversedTransfers
diff --git a/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/Transfer.java b/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/Transfer.java
index 648343b9b0f..7e66498f349 100644
--- a/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/Transfer.java
+++ b/application/src/main/java/org/opentripplanner/routing/algorithm/raptoradapter/transit/Transfer.java
@@ -1,9 +1,8 @@
 package org.opentripplanner.routing.algorithm.raptoradapter.transit;
 
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Sets;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Optional;
@@ -35,20 +34,20 @@ public class Transfer {
 
   private final List<Edge> edges;
 
-  private final ImmutableSet<StreetMode> modes;
+  private final Set<StreetMode> modes;
 
   public Transfer(int toStop, List<Edge> edges, EnumSet<StreetMode> modes) {
     this.toStop = toStop;
     this.edges = edges;
     this.distanceMeters = (int) edges.stream().mapToDouble(Edge::getDistanceMeters).sum();
-    this.modes = Sets.immutableEnumSet(modes);
+    this.modes = Collections.unmodifiableSet(modes);
   }
 
   public Transfer(int toStopIndex, int distanceMeters, EnumSet<StreetMode> modes) {
     this.toStop = toStopIndex;
     this.distanceMeters = distanceMeters;
     this.edges = null;
-    this.modes = Sets.immutableEnumSet(modes);
+    this.modes = Collections.unmodifiableSet(modes);
   }
 
   public List<Coordinate> getCoordinates() {
@@ -76,8 +75,8 @@ public List<Edge> getEdges() {
     return edges;
   }
 
-  public ImmutableSet<StreetMode> getModes() {
-    return modes;
+  public boolean allowsMode(StreetMode mode) {
+    return modes.contains(mode);
   }
 
   public Optional<RaptorTransfer> asRaptorTransfer(StreetSearchRequest request) {