diff --git a/src/edu/kit/informatik/ModelRailwaySimulation.java b/src/edu/kit/informatik/ModelRailwaySimulation.java
index 5eed11f..1bce758 100644
--- a/src/edu/kit/informatik/ModelRailwaySimulation.java
+++ b/src/edu/kit/informatik/ModelRailwaySimulation.java
@@ -518,24 +518,6 @@ public class ModelRailwaySimulation {
 
     private ArrayList<Set<Train>> getCollisionsOfOneStep() {
         ArrayList<Set<Train>> collisions = new ArrayList<>();
-        // check touching trains
-        /*
-        for (Train train : trains) {
-            if (!train.isPlaced()) {
-                continue;
-            }
-            for (Train otherTrain : trains) {
-                if (!otherTrain.isPlaced() || train == otherTrain) {
-                    continue;
-                }
-                if (train.getFrontPosition().equals(otherTrain.getFrontPosition())) {
-                    train.removeFromRails();
-                    otherTrain.removeFromRails();
-                    collisions.add(Arrays.asList(train, otherTrain));
-                }
-            }
-        }
-        */
         Map<Train, Set<Rail>> occupiedRails = new HashMap<>();
         for (Train train : trains) {
             if (train.isPlaced()) {
@@ -570,9 +552,12 @@ public class ModelRailwaySimulation {
                 continue; // already included in collision
             }
             Set<Rail> occupiedByThisTrain = nextOccupiedRails.get(train);
-            trains.stream().filter((x) -> x != train && x.isPlaced()).forEach((otherTrain) -> {
+            trains.stream().filter((x) -> x != train).forEach((otherTrain) -> {
                 Set<Rail> occupiedByOtherTrainPreviously = occupiedRails.get(otherTrain);
                 Set<Rail> occupiedByOtherTrain = nextOccupiedRails.get(otherTrain);
+                if (occupiedByOtherTrain == null || occupiedByOtherTrainPreviously == null) {
+                    return;
+                }
                 boolean anyIntersection = occupiedByOtherTrain.stream().anyMatch(occupiedByThisTrain::contains)
                         || occupiedByOtherTrainPreviously.stream().anyMatch(occupiedByThisTrain::contains);
                 if (anyIntersection) {
@@ -589,6 +574,9 @@ public class ModelRailwaySimulation {
                             }
                         }
                     }
+                    if (existingCollision == null) {
+                        collisions.add(new HashSet<>(Arrays.asList(train, otherTrain)));
+                    }
                 }
             });
         }
@@ -597,24 +585,6 @@ public class ModelRailwaySimulation {
 
     private ArrayList<Set<Train>> getCollisionsOfOneReverseStep() {
         ArrayList<Set<Train>> collisions = new ArrayList<>();
-        // check touching trains
-        /*
-        for (Train train : trains) {
-            if (!train.isPlaced()) {
-                continue;
-            }
-            for (Train otherTrain : trains) {
-                if (!otherTrain.isPlaced() || train == otherTrain) {
-                    continue;
-                }
-                if (train.getBackPosition().equals(otherTrain.getBackPosition())) {
-                    train.removeFromRails();
-                    otherTrain.removeFromRails();
-                    collisions.add(new HashSet<>(Arrays.asList(train, otherTrain)));
-                }
-            }
-        }
-        */
         Map<Train, Set<Rail>> occupiedRails = new HashMap<>();
         for (Train train : trains) {
             if (train.isPlaced()) {
@@ -649,9 +619,12 @@ public class ModelRailwaySimulation {
                 continue; // already included in collision
             }
             Set<Rail> occupiedByThisTrain = nextOccupiedRails.get(train);
-            trains.stream().filter((x) -> x != train && train.isPlaced()).forEach((otherTrain) -> {
+            trains.stream().filter((x) -> x != train).forEach((otherTrain) -> {
                 Set<Rail> occupiedByOtherTrainPreviously = occupiedRails.get(otherTrain);
                 Set<Rail> occupiedByOtherTrain = nextOccupiedRails.get(otherTrain);
+                if (occupiedByOtherTrain == null || occupiedByOtherTrainPreviously == null) {
+                    return;
+                }
                 boolean anyIntersection = occupiedByOtherTrain.stream().anyMatch(occupiedByThisTrain::contains)
                         || occupiedByOtherTrainPreviously.stream().anyMatch(occupiedByThisTrain::contains);
                 if (anyIntersection) {