diff --git a/app/src/main/java/de/hems/trafficsim/MainActivity.java b/app/src/main/java/de/hems/trafficsim/MainActivity.java
index a693a4d..e2581c5 100644
--- a/app/src/main/java/de/hems/trafficsim/MainActivity.java
+++ b/app/src/main/java/de/hems/trafficsim/MainActivity.java
@@ -1,9 +1,11 @@
 package de.hems.trafficsim;
 
 import androidx.appcompat.app.AppCompatActivity;
+import androidx.constraintlayout.widget.ConstraintLayout;
 
 import android.os.Bundle;
 import android.view.View;
+import android.widget.Button;
 import android.widget.TextView;
 
 import java.util.Observable;
@@ -12,41 +14,75 @@ import java.util.Observer;
 public class MainActivity extends AppCompatActivity implements Observer {
 
     protected Track track;
-    protected VehicleTimeRecord records;
+    protected TrackView trackView;
+    protected Worker worker;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
-        this.track = new Track(20);
-        this.records = null;
+        this.track = new Track(25, 100);
+        this.trackView = new TrackView(this, this.track);
         this.track.addObserver(this);
-
+        ConstraintLayout layout = (ConstraintLayout) findViewById(R.id.constr_layout);
+        layout.addView(this.trackView);
     }
 
     @Override
     public void update(Observable observable, Object o) {
-        String s = "";
-        for (Vehicle v: this.track.getVehicles()){
-            s+= "Vehicle " + v.id + "   |   "
-                    + "Pos = " + v.getPosition() + "   |   "
-                    + "Vel = " + v.getCurVelocity()+ "   |   "
-                    + "\n";
-            ;
-        }
-        String t = "";      //vtr arraylist to string
-        String text = s + "\n" + t;
-        TextView view = (TextView) findViewById(R.id.debugTextView);
-        view.setText(text);
-        view.invalidate();
+        final Track trackRef = this.track;
+        final TrackView viewRef = this.trackView;
+        runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                String s = "";
+                for (Vehicle v: trackRef.getVehicles()){
+                    s+= "Vehicle " + v.id + "   |   "
+                            + "Pos = " + v.getPosition() + "   |   "
+                            + "Vel = " + v.getCurVelocity()+ "   |   "
+                            + "\n";
+                    ;
+                }
+                TextView view = (TextView) findViewById(R.id.debugTextView);
+                view.setText(s);
+                view.invalidate();
+                viewRef.invalidate();
+            }
+        });
+
     }
 
-    public void onStepButtonClick (View view) {
-        for (int j = 0; j < 1; j++) {
+    public void onStepButtonClick(View view) {
+        //for (int j = 0; j < 3000; j++) {
             this.track.timeElapse(50);
-        }
+        //}
     }
 
+    public void onPlayButtonClick(View view) {
+        Button playButton = (Button) findViewById(R.id.playButton);
+        playButton.setEnabled(false);
+        Button stepButton = (Button) findViewById(R.id.stepButton);
+        stepButton.setEnabled(false);
+        Button stopButton = (Button) findViewById(R.id.stopButton);
+        stopButton.setEnabled(true);
 
-}
+        this.worker = new Worker(track);
+        this.worker.start();
+    }
 
+    public void onStopButtonClick(View view) {
+        Button playButton = (Button) findViewById(R.id.playButton);
+        playButton.setEnabled(true);
+        Button stepButton = (Button) findViewById(R.id.stepButton);
+        stepButton.setEnabled(true);
+        Button stopButton = (Button) findViewById(R.id.stopButton);
+        stopButton.setEnabled(false);
+
+        this.worker.setStop(true);
+        try {
+            this.worker.join();
+        } catch (InterruptedException ex) {
+
+        }
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/de/hems/trafficsim/Track.java b/app/src/main/java/de/hems/trafficsim/Track.java
index aaf508c..06f9ed6 100644
--- a/app/src/main/java/de/hems/trafficsim/Track.java
+++ b/app/src/main/java/de/hems/trafficsim/Track.java
@@ -8,14 +8,18 @@ import java.util.Observable;
 public class Track extends Observable {
     protected List<Vehicle> vehicles;
     protected List<List<VehicleTimeRecord>> vtr_list;
-
+    protected float trackLength;
 
     public List<Vehicle> getVehicles() {
-
         return vehicles;
     }
 
-    public Track(int numberVehicles) {
+    public float getTrackLength() {
+        return trackLength;
+    }
+
+    public Track(int numberVehicles, float trackLength) {
+        this.trackLength = trackLength;
         this.vehicles = createVehiclesList(numberVehicles);
         this.vtr_list = new LinkedList<>();
     }
@@ -23,14 +27,14 @@ public class Track extends Observable {
     protected List<Vehicle> createVehiclesList(int numberVehicles){
         List<Vehicle> result = new ArrayList<>();
         for(int i=0;i<numberVehicles;i++){
-            Vehicle vehicle = new Vehicle(i, i, 5, 0.2f);
+            Vehicle vehicle = new Vehicle(i, i, 5, 0.2f, this.trackLength);
             result.add(vehicle);
         }
 
         return result;
     }
 
-    public void timeElapse(int timeStep) {
+    public void timeElapse(float timeStep) {
         for(int i=0; i<vehicles.size();i++) {
             Vehicle v = vehicles.get(i);
             int forerunnerIndex = i + 1;
@@ -40,7 +44,7 @@ public class Track extends Observable {
             Vehicle forerunner = vehicles.get(forerunnerIndex);
             float distanceForerunner = forerunner.getPosition() - v.getPosition() - 1;
             if(distanceForerunner < 0.0){
-                distanceForerunner += 50;
+                distanceForerunner += this.trackLength;
             }
             v.updateVelocity(distanceForerunner);
         }
diff --git a/app/src/main/java/de/hems/trafficsim/TrackView.java b/app/src/main/java/de/hems/trafficsim/TrackView.java
new file mode 100644
index 0000000..20aee09
--- /dev/null
+++ b/app/src/main/java/de/hems/trafficsim/TrackView.java
@@ -0,0 +1,51 @@
+package de.hems.trafficsim;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.view.View;
+import android.view.ViewGroup;
+
+public class TrackView extends View {
+    protected Paint paint;
+    protected Track track;
+    protected int pixelPerVehicle;
+
+    public TrackView(Context context, Track track) {
+        super(context);
+        this.track = track;
+        this.paint = new Paint();
+        paint.setColor(Color.BLACK);
+        paint.setStyle(Paint.Style.FILL_AND_STROKE);
+    }
+
+    protected int getColor(float curVelocity, float maxVelocity) {
+        float perc = curVelocity / maxVelocity;
+        if (perc <= 0.5) {
+            int red = ((int) (2*perc*0xFF)) << 16;
+            int green = ((int)0xFF) << 8;
+            int blue = 0;
+            return 0xff000000 | red | green | blue;
+        } else {
+            int red = ((int)(0xFF)) << 16;
+            int green = ((int)(0xFF-0xFF*(perc-0.5)*2)) << 8;
+            int blue = 0;
+            return 0xff000000 | red | green | blue;
+        }
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        this.pixelPerVehicle = (int) (this.getWidth() / this.track.getTrackLength());
+        //super.onDraw(canvas);
+        int i = 0;
+        for (Vehicle v : this.track.getVehicles()) {
+            int left = (int) (this.pixelPerVehicle * v.getPosition());
+            this.paint.setColor(getColor(v.getCurVelocity(), v.getMaxVelocity()));
+            canvas.drawRect(left, 0, left + this.pixelPerVehicle - 1,
+                    20, this.paint);
+            i++;
+        }
+    }
+}
diff --git a/app/src/main/java/de/hems/trafficsim/Vehicle.java b/app/src/main/java/de/hems/trafficsim/Vehicle.java
index 5e2792d..e6fbb0b 100644
--- a/app/src/main/java/de/hems/trafficsim/Vehicle.java
+++ b/app/src/main/java/de/hems/trafficsim/Vehicle.java
@@ -8,14 +8,16 @@ public class Vehicle {
     protected float curVelocity;
     protected float maxVelocity;
     protected float brakeProp;
+    protected float trackLength;
 
 
-    public Vehicle(int id, int position, float maxVelocity, float brakeProp) {
+    public Vehicle(int id, int position, float maxVelocity, float brakeProp, float trackLength) {
         this.id = id;
         this.position = position;
         this.maxVelocity = maxVelocity;
         this.brakeProp = brakeProp;
         this.curVelocity = 0;
+        this.trackLength = trackLength;
 
     }
 
@@ -27,6 +29,10 @@ public class Vehicle {
         return curVelocity;
     }
 
+    public float getMaxVelocity() {
+        return maxVelocity;
+    }
+
     public void updateVelocity(float distanceForerunner) {
         Random random = new Random();
 
@@ -45,7 +51,7 @@ public class Vehicle {
     }
 
     public void timeElapse(float timeStep) {
-        position = (position + curVelocity) % 50;
+        position = (position + curVelocity) % this.trackLength;
     }
 
 }
diff --git a/app/src/main/java/de/hems/trafficsim/Worker.java b/app/src/main/java/de/hems/trafficsim/Worker.java
new file mode 100644
index 0000000..862f60f
--- /dev/null
+++ b/app/src/main/java/de/hems/trafficsim/Worker.java
@@ -0,0 +1,22 @@
+package de.hems.trafficsim;
+
+public class Worker extends Thread {
+    protected Track track;
+    protected boolean stop;
+    public Worker(Track track) {
+        super();
+        this.track = track;
+        this.stop = false;
+    }
+
+    void setStop(boolean stop) {
+        this.stop = stop;
+    }
+
+    @Override
+    public void run() {
+        while (!stop) {
+            this.track.timeElapse(50);
+        }
+    }
+}
diff --git a/app/src/main/res/layout/activity_main.xml b/app/src/main/res/layout/activity_main.xml
index 5d5c8ca..4cb5ebd 100644
--- a/app/src/main/res/layout/activity_main.xml
+++ b/app/src/main/res/layout/activity_main.xml
@@ -2,10 +2,24 @@
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/constr_layout"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity">
 
+    <Button
+        android:id="@+id/stopButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="16dp"
+        android:enabled="false"
+        android:onClick="onStopButtonClick"
+        android:text="Stop"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.95"
+        app:layout_constraintStart_toStartOf="parent" />
+
     <TextView
         android:id="@+id/debugTextView"
         android:layout_width="wrap_content"
@@ -22,9 +36,21 @@
         android:layout_height="wrap_content"
         android:layout_marginBottom="16dp"
         android:onClick="onStepButtonClick"
-        android:text="Button"
+        android:text="Step"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintHorizontal_bias="0.5"
         app:layout_constraintStart_toStartOf="parent" />
+
+    <Button
+        android:id="@+id/playButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="16dp"
+        android:onClick="onPlayButtonClick"
+        android:text="Play"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.049"
+        app:layout_constraintStart_toStartOf="parent" />
 </androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file