diff --git a/InnerDetector/InDetSimEvent/InDetSimEvent/TRTHitIdHelper.h b/InnerDetector/InDetSimEvent/InDetSimEvent/TRTHitIdHelper.h
index 7fdec74378944b1d91917cc084be6652098c2245..21ca9cfc3bbcd12c6ceacdec05898e70058ebd50 100755
--- a/InnerDetector/InDetSimEvent/InDetSimEvent/TRTHitIdHelper.h
+++ b/InnerDetector/InDetSimEvent/InDetSimEvent/TRTHitIdHelper.h
@@ -1,16 +1,16 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
 */
 
 #ifndef INDETSIMEVENT_TRTHITIDHELPER
 #define INDETSIMEVENT_TRTHITIDHELPER
 
 //
-// This is a helper class to build an identifing integer used by 
+// This is a helper class to build an identifing integer used by
 // the simulation. It inherits from HitIdHelper, in order to get
-// all the packing and shifting for free. 
-// The class is a singleton and a static GetHelper() is provided 
-// the constructor calls the Initialize() method which sets all the 
+// all the packing and shifting for free.
+// The class is a singleton and a static GetHelper() is provided
+// the constructor calls the Initialize() method which sets all the
 // field dimensions
 // Methods are provided to get access to the TRT Geometry
 // description
@@ -26,39 +26,39 @@ class TRTHitIdHelper : HitIdHelper {
  public:
   //
   // Access to the helper
-  static TRTHitIdHelper* GetHelper();  
+  static TRTHitIdHelper* GetHelper();
   //
   // Info retrieval:
   // Barrel or Endcap
-  bool isBarrel(const int& hid);
-  bool isEndcap(const int& hid);
+  bool isBarrel(const int& hid) const;
+  bool isEndcap(const int& hid) const;
   //
-  // Positive or negative side 
-  bool isPositive(const int& hid);
-  bool isNegative(const int& hid);
+  // Positive or negative side
+  bool isPositive(const int& hid) const;
+  bool isNegative(const int& hid) const;
 
   // Ring or Wheel
-  int getRingWheel(const int& hid);
+  int getRingWheel(const int& hid) const;
 
   // PhiSector
-  int getPhiSector(const int& hid);
-  
+  int getPhiSector(const int& hid) const;
+
   // Layer Plane
-  int getLayerPlane(const int& hid);
+  int getLayerPlane(const int& hid) const;
 
   // straw
-  int getStraw(const int& hid);
+  int getStraw(const int& hid) const;
   //
   // Info packing:
-  int buildHitId(const int, const int, const int, const int, const int, const int);
+  int buildHitId(const int, const int, const int, const int, const int, const int) const;
 
  private:
   //
   // private constructor to have a singleton
-  TRTHitIdHelper(); 
+  TRTHitIdHelper();
   //
   // Initialize the helper, only called by the constructor
-  void Initialize();  
+  void Initialize();
 };
 
 #endif // INDETSIMEVENT_TRTHITIDHELPER
diff --git a/InnerDetector/InDetSimEvent/src/TRTHitIdHelper.cxx b/InnerDetector/InDetSimEvent/src/TRTHitIdHelper.cxx
index c0c4a9bf5eecba74ce819882821e55ebc4cfde62..d424031d8f4206a81758929d8e10317f61ece160 100755
--- a/InnerDetector/InDetSimEvent/src/TRTHitIdHelper.cxx
+++ b/InnerDetector/InDetSimEvent/src/TRTHitIdHelper.cxx
@@ -1,10 +1,10 @@
 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
 */
 
 #include "InDetSimEvent/TRTHitIdHelper.h"
 
-// 
+//
 // private constructor
 TRTHitIdHelper::TRTHitIdHelper() :HitIdHelper() {
   Initialize();
@@ -22,75 +22,65 @@ void TRTHitIdHelper::Initialize() {
   InitializeField("RingWheel",0,31);
   InitializeField("PositiveNegative",0,1);
   InitializeField("BarrelEndcap",0,1);
-} 
+}
 
   // Info retrieval:
   // Barrel or Endcap
-bool TRTHitIdHelper::isBarrel(const int& hid){
-  this->SetID(hid);
-  int ps = this->GetFieldValue("BarrelEndcap");
+bool TRTHitIdHelper::isBarrel(const int& hid) const {
+  int ps = this->GetFieldValue("BarrelEndcap", hid);
   if (ps ==0 ) return true;
   else return false;
 }
 
-bool TRTHitIdHelper::isEndcap(const int& hid){
-  this->SetID(hid);
-  int ps = this->GetFieldValue("BarrelEndcap");
+bool TRTHitIdHelper::isEndcap(const int& hid) const {
+  int ps = this->GetFieldValue("BarrelEndcap", hid);
   if (ps ==0 ) return false;
   else return true;
-}  
+}
 
 // Positive or Negative
-bool TRTHitIdHelper::isPositive(const int& hid){
-  this->SetID(hid);
-  int ps = this->GetFieldValue("PositiveNegative");
+bool TRTHitIdHelper::isPositive(const int& hid) const {
+  int ps = this->GetFieldValue("PositiveNegative", hid);
   if (ps ==0 ) return true;
   else return false;
-}  
-bool TRTHitIdHelper::isNegative(const int& hid){
-  this->SetID(hid);
-  int ps = this->GetFieldValue("PositiveNegative");
+}
+bool TRTHitIdHelper::isNegative(const int& hid) const {
+  int ps = this->GetFieldValue("PositiveNegative", hid);
   if (ps ==0 ) return false;
   else return true;
-}  
+}
 
 // Ring/Wheel
-int TRTHitIdHelper::getRingWheel(const int& hid) {
-  this->SetID(hid);
-  return this->GetFieldValue("RingWheel");
-}  
+int TRTHitIdHelper::getRingWheel(const int& hid) const {
+  return this->GetFieldValue("RingWheel", hid);
+}
 
 // Phi Sector
-int TRTHitIdHelper::getPhiSector(const int& hid)  {
-  this->SetID(hid);
-  return this->GetFieldValue("PhiSector");
+int TRTHitIdHelper::getPhiSector(const int& hid) const {
+  return this->GetFieldValue("PhiSector", hid);
 }
 
 // layer/plane
-int TRTHitIdHelper::getLayerPlane(const int& hid) {
-  this->SetID(hid);
-  return this->GetFieldValue("LayerPlane");
+int TRTHitIdHelper::getLayerPlane(const int& hid) const {
+  return this->GetFieldValue("LayerPlane", hid);
 }
-  
+
 // straw
-int TRTHitIdHelper::getStraw(const int& hid) {
-  this->SetID(hid);
-  return this->GetFieldValue("Straw");
+int TRTHitIdHelper::getStraw(const int& hid) const {
+  return this->GetFieldValue("Straw", hid);
 }
 
 
 //
 // Info packing:
 int TRTHitIdHelper::buildHitId(const int BrlECap, const int PosNeg, const int RingWheel,
-			      const int PhiS, const int LayerPlane, const int Straw) {
-  this->SetID(0);
-  this->SetFieldValue("BarrelEndcap",     BrlECap);
-  this->SetFieldValue("PositiveNegative", PosNeg);
-  this->SetFieldValue("RingWheel",        RingWheel);
-  this->SetFieldValue("PhiSector",        PhiS);
-  this->SetFieldValue("LayerPlane",       LayerPlane);
-  this->SetFieldValue("Straw",            Straw);
-  return this->GetID();
+                              const int PhiS, const int LayerPlane, const int Straw) const {
+  int theID(0);
+  this->SetFieldValue("BarrelEndcap",     BrlECap, theID);
+  this->SetFieldValue("PositiveNegative", PosNeg, theID);
+  this->SetFieldValue("RingWheel",        RingWheel, theID);
+  this->SetFieldValue("PhiSector",        PhiS, theID);
+  this->SetFieldValue("LayerPlane",       LayerPlane, theID);
+  this->SetFieldValue("Straw",            Straw, theID);
+  return theID;
 }
-
-