diff --git a/src/data/Track.cpp b/src/data/Track.cpp
index 5cd7585..b1b3627 100644
--- a/src/data/Track.cpp
+++ b/src/data/Track.cpp
@@ -13,6 +13,7 @@ const uint64_t Track::MAX_INDEX = 65535;
 const std::string Track::STATE_ACTIVE = "ACTIVE";
 const std::string Track::STATE_TENTATIVE = "TENTATIVE";
 const std::string Track::STATE_COASTING = "COASTING";
+const std::string Track::STATE_ASSOCIATED = "ASSOCIATED";
 
 // constructor
 Track::Track()
@@ -33,7 +34,7 @@ std::string Track::uint2hex(uint64_t number)
 
 void Track::set_state(uint64_t index, std::string _state)
 {
-  state.at(index) = _state;
+  state.at(index).push_back(_state);
 }
 
 void Track::set_current(uint64_t index, Detection smoothed)
@@ -57,7 +58,7 @@ uint64_t Track::get_nActive()
   uint64_t n = 0;
   for (size_t i = 0; i < id.size(); i++)
   {
-    if (state.at(i) == STATE_ACTIVE)
+    if (get_state(i) == STATE_ACTIVE)
     {
       n++;
     }
@@ -70,7 +71,7 @@ uint64_t Track::get_nTentative()
   uint64_t n = 0;
   for (size_t i = 0; i < id.size(); i++)
   {
-    if (state.at(i) == STATE_TENTATIVE)
+    if (get_state(i) == STATE_TENTATIVE)
     {
       n++;
     }
@@ -95,7 +96,7 @@ double Track::get_acceleration(uint64_t index)
 
 std::string Track::get_state(uint64_t index)
 {
-  return state.at(index);
+  return state.at(index).at(state.at(index).size()-1);
 }
 
 uint64_t Track::get_nInactive(uint64_t index)
@@ -106,7 +107,9 @@ uint64_t Track::get_nInactive(uint64_t index)
 uint64_t Track::add(Detection initial)
 {
   id.push_back(uint2hex(iNext));
-  state.push_back(STATE_TENTATIVE);
+  std::vector<std::string> _state;
+  _state.push_back(STATE_TENTATIVE);
+  state.push_back(_state);
   current.push_back(initial);
   acceleration.push_back(0);
   std::vector<Detection> _associated;
@@ -121,6 +124,27 @@ uint64_t Track::add(Detection initial)
   return id.size()-1;
 }
 
+void Track::promote(uint64_t index, uint32_t m, uint32_t n)
+{
+  if (state.at(index).size() >= n)
+  {
+    uint32_t _m = 0;
+    for (size_t i = state.at(index).size()-n; i < state.at(index).size(); i++) 
+    {
+      if (state.at(index).at(i) == STATE_ACTIVE || 
+        state.at(index).at(i) == STATE_ASSOCIATED)
+      {
+        _m++;
+      }
+    }
+    // promote track to ACTIVE if passes test
+    if (_m >= m)
+    {
+      state.at(index).at(state.at(index).size()-1) = STATE_ACTIVE;
+    }
+  }
+}
+
 void Track::remove(uint64_t index)
 {
   id.erase(id.begin() + index);
@@ -141,7 +165,7 @@ std::string Track::to_json(uint64_t timestamp)
   rapidjson::Value value;
   for (int i = 0; i < get_n(); i++)
   {
-    if (state.at(i) != STATE_TENTATIVE)
+    if (get_state(i) != STATE_TENTATIVE)
     {
       value = rapidjson::StringRef(id.at(i).c_str());
       arrayId.PushBack(value, allocator);
diff --git a/src/data/Track.h b/src/data/Track.h
index d6d0b8b..87e42ea 100644
--- a/src/data/Track.h
+++ b/src/data/Track.h
@@ -2,9 +2,10 @@
 /// @class Track
 /// @brief A class to store track data.
 /// @details The ID is 4 digit hexadecimal with 16^4 = 65536 combinations.
-/// @details The state can be TENTATIVE, ACTIVE or COASTING.
+/// @details The state can be TENTATIVE, ASSOCIATED, ACTIVE or COASTING.
 /// @details Associated detections use null detections when no updates.
 /// @author 30hours
+/// @todo I feel promote() should be implemented in the tracker.
 
 #ifndef TRACK_H
 #define TRACK_H
@@ -19,11 +20,10 @@ class Track
 {
 private:
   /// @brief Track ID (4 digit alpha-numeric).
-  //std::unique_ptr<std::vector<std::string>> id;
   std::vector<std::string> id;
 
-  /// @brief Current state (see VALID_STATE).
-  std::vector<std::string> state;
+  /// @brief State history for each track.
+  std::vector<std::vector<std::string>> state;
 
   /// @brief Curent track position.
   std::vector<Detection> current;
@@ -53,6 +53,9 @@ private:
   /// @brief String for state COASTING.
   static const std::string STATE_COASTING;
 
+  /// @brief String for state ASSOCIATED.
+  static const std::string STATE_ASSOCIATED;
+
 public:
   /// @brief Constructor.
   /// @return The object.
@@ -68,7 +71,7 @@ public:
   /// @return hex Hexadecimal number.
   std::string uint2hex(uint64_t number);
 
-  /// @brief Set the state of a track.
+  /// @brief Set the state of the latest tracklet.
   /// @param index Index of track to change.
   /// @param state Updated state.
   /// @return Void.
@@ -134,6 +137,12 @@ public:
   /// @return Index of last track.
   uint64_t add(Detection initial);
 
+  /// @brief Promote track to state ACTIVE if applicable.
+  /// @details Uses M of N rule for ACTIVE tracks.
+  /// @param index Index of track to change.
+  /// @return Void.
+  void promote(uint64_t index, uint32_t m, uint32_t n);
+
   /// @brief Remove track based on index.
   /// @param index Index of track to remove.
   /// @return Void.
diff --git a/src/process/tracker/Tracker.cpp b/src/process/tracker/Tracker.cpp
index 8fae686..7fe4002 100644
--- a/src/process/tracker/Tracker.cpp
+++ b/src/process/tracker/Tracker.cpp
@@ -81,13 +81,14 @@ void Tracker::update(Detection *detection, uint64_t current)
       {
         Detection associated(delay[j], doppler[j], snr[j]);
         track.set_current(i, associated);
-        state = "ACTIVE";
-        track.set_state(i, state);
         track.set_acceleration(i, (doppler[j]-dopplerTrack)/T);
         track.set_nInactive(i, 0);
         doNotInitiate[j] = true;
+        state = "ASSOCIATED";
+        track.set_state(i, state);
+        // check for track promotion
+        track.promote(i, m, n);
         break;
-        // todo: check for track promotion
       }
     }
 
@@ -98,6 +99,10 @@ void Tracker::update(Detection *detection, uint64_t current)
       state = "COASTING";
       track.set_state(i, state);
     }
+    else
+    {
+      track.set_state(i, track.get_state(i));
+    }
     track.set_nInactive(i, track.get_nInactive(i)+1);
 
     // remove if tentative or coasting too long