diff --git a/Framework/Cascade/Cascade.h b/Framework/Cascade/Cascade.h
index 75f29e4ed51bc70d7d31d4917ef4c186baee4bef..f9ec0beb0e40df08a16595bee6be8dc0048cff94 100644
--- a/Framework/Cascade/Cascade.h
+++ b/Framework/Cascade/Cascade.h
@@ -153,7 +153,7 @@ namespace corsika::cascade {
 
       // determine combined total interaction length (inverse)
       InverseGrammageType const total_inv_lambda =
-          fProcessSequence.GetTotalInverseInteractionLength(vParticle, step);
+          fProcessSequence.GetTotalInverseInteractionLength(vParticle);
 
       // sample random exponential step length in grammage
       corsika::random::ExponentialDistribution expDist(1 / total_inv_lambda);
@@ -242,13 +242,14 @@ namespace corsika::cascade {
         if (min_distance == distance_interact) {
           std::cout << "collide" << std::endl;
 
-          InverseGrammageType const actual_inv_length =
-              fProcessSequence.GetTotalInverseInteractionLength(vParticle, step);
+          InverseGrammageType const current_inv_length =
+              fProcessSequence.GetTotalInverseInteractionLength(vParticle);
 
-          random::UniformRealDistribution<InverseGrammageType> uniDist(actual_inv_length);
+          random::UniformRealDistribution<InverseGrammageType> uniDist(
+              current_inv_length);
           const auto sample_process = uniDist(fRNG);
           InverseGrammageType inv_lambda_count = 0. * meter * meter / gram;
-          fProcessSequence.SelectInteraction(vParticle, projectile, step, sample_process,
+          fProcessSequence.SelectInteraction(vParticle, projectile, sample_process,
                                              inv_lambda_count);
         } else if (min_distance == distance_decay) {
           std::cout << "decay" << std::endl;
diff --git a/Framework/Cascade/testCascade.cc b/Framework/Cascade/testCascade.cc
index 89fd65ef42150149a9c0ffbd7183fed865ba659d..f29d1af9fba4c01c6452fc2dc026df7ff99f2c42 100644
--- a/Framework/Cascade/testCascade.cc
+++ b/Framework/Cascade/testCascade.cc
@@ -69,8 +69,8 @@ public:
   ProcessSplit(GrammageType const X0)
       : fX0(X0) {}
 
-  template <typename Particle, typename Track>
-  corsika::units::si::GrammageType GetInteractionLength(Particle&, Track&) const {
+  template <typename Particle>
+  corsika::units::si::GrammageType GetInteractionLength(Particle const&) const {
     return fX0;
   }
 
diff --git a/Framework/ProcessSequence/InteractionProcess.h b/Framework/ProcessSequence/InteractionProcess.h
index 27ad9c222d5ce644d6b344a469edaf8e717fcf87..a9b4b9fca306e865a85ac94ae6a9878ce7f0057d 100644
--- a/Framework/ProcessSequence/InteractionProcess.h
+++ b/Framework/ProcessSequence/InteractionProcess.h
@@ -38,13 +38,12 @@ namespace corsika::process {
     template <typename Particle>
     EProcessReturn DoInteraction(Particle&);
 
-    template <typename Particle, typename Track>
-    corsika::units::si::GrammageType GetInteractionLength(Particle& p, Track& t);
+    template <typename TParticle>
+    corsika::units::si::GrammageType GetInteractionLength(TParticle& p);
 
-    template <typename Particle, typename Track>
-    corsika::units::si::InverseGrammageType GetInverseInteractionLength(Particle& p,
-                                                                        Track& t) {
-      return 1. / GetRef().GetInteractionLength(p, t);
+    template <typename TParticle>
+    corsika::units::si::InverseGrammageType GetInverseInteractionLength(TParticle& p) {
+      return 1. / GetRef().GetInteractionLength(p);
     }
   };
 
diff --git a/Framework/ProcessSequence/ProcessSequence.h b/Framework/ProcessSequence/ProcessSequence.h
index 3bd759c04a97e55360c87473cc4457159bd967fa..55eb43ba795c35d04654a5256232221fa4c900b5 100644
--- a/Framework/ProcessSequence/ProcessSequence.h
+++ b/Framework/ProcessSequence/ProcessSequence.h
@@ -47,9 +47,19 @@ namespace corsika::process {
 
   // this is a marker to track which BaseProcess is also a ProcessSequence
   template <typename T>
-  struct is_process_sequence {
-    static const bool value = false;
-  };
+  struct is_process_sequence : std::false_type {};
+
+  template <typename T>
+  bool constexpr is_process_sequence_v = is_process_sequence<T>::value;
+
+  namespace switch_process {
+    template <typename A, typename B>
+    class SwitchProcess; // fwd-decl.
+  }
+
+  template <typename A, typename B>
+  struct is_process_sequence<switch_process::SwitchProcess<A, B>>
+      : std::true_type {};
 
   /**
      T1 and T2 are both references if possible (lvalue), otherwise
@@ -57,11 +67,14 @@ namespace corsika::process {
      rvalue as well as lvalue Processes in the ProcessSequence.
    */
   template <typename T1, typename T2>
-  class ProcessSequence : public BaseProcess<ProcessSequence<T1, T2> > {
+  class ProcessSequence : public BaseProcess<ProcessSequence<T1, T2>> {
 
     using T1type = typename std::decay<T1>::type;
     using T2type = typename std::decay<T2>::type;
 
+    static bool constexpr t1ProcSeq = is_process_sequence_v<T1type>;
+    static bool constexpr t2ProcSeq = is_process_sequence_v<T2type>;
+
   public:
     T1 A; // this is a reference, if possible
     T2 B; // this is a reference, if possible
@@ -78,13 +91,13 @@ namespace corsika::process {
                                       VTNType const& to) {
       EProcessReturn ret = EProcessReturn::eOk;
 
-      if constexpr (std::is_base_of<BoundaryCrossingProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<BoundaryCrossingProcess<T1type>, T1type> ||
+                    t1ProcSeq) {
         ret |= A.DoBoundaryCrossing(p, from, to);
       }
 
-      if constexpr (std::is_base_of<BoundaryCrossingProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<BoundaryCrossingProcess<T2type>, T2type> ||
+                    t2ProcSeq) {
         ret |= B.DoBoundaryCrossing(p, from, to);
       }
 
@@ -94,12 +107,10 @@ namespace corsika::process {
     template <typename TParticle, typename TTrack>
     EProcessReturn DoContinuous(TParticle& vP, TTrack& vT) {
       EProcessReturn ret = EProcessReturn::eOk;
-      if constexpr (std::is_base_of<ContinuousProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<ContinuousProcess<T1type>, T1type> || t1ProcSeq) {
         ret |= A.DoContinuous(vP, vT);
       }
-      if constexpr (std::is_base_of<ContinuousProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<ContinuousProcess<T2type>, T2type> || t2ProcSeq) {
         ret |= B.DoContinuous(vP, vT);
       }
       return ret;
@@ -108,12 +119,10 @@ namespace corsika::process {
     template <typename TSecondaries>
     EProcessReturn DoSecondaries(TSecondaries& vS) {
       EProcessReturn ret = EProcessReturn::eOk;
-      if constexpr (std::is_base_of<SecondariesProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<SecondariesProcess<T1type>, T1type> || t1ProcSeq) {
         ret |= A.DoSecondaries(vS);
       }
-      if constexpr (std::is_base_of<SecondariesProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<SecondariesProcess<T2type>, T2type> || t2ProcSeq) {
         ret |= B.DoSecondaries(vS);
       }
       return ret;
@@ -121,12 +130,10 @@ namespace corsika::process {
 
     bool CheckStep() {
       bool ret = false;
-      if constexpr (std::is_base_of<StackProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<StackProcess<T1type>, T1type> || t1ProcSeq) {
         ret |= A.CheckStep();
       }
-      if constexpr (std::is_base_of<StackProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<StackProcess<T2type>, T2type> || t2ProcSeq) {
         ret |= B.CheckStep();
       }
       return ret;
@@ -135,12 +142,10 @@ namespace corsika::process {
     template <typename TStack>
     EProcessReturn DoStack(TStack& vS) {
       EProcessReturn ret = EProcessReturn::eOk;
-      if constexpr (std::is_base_of<StackProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<StackProcess<T1type>, T1type> || t1ProcSeq) {
         if (A.CheckStep()) { ret |= A.DoStack(vS); }
       }
-      if constexpr (std::is_base_of<StackProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<StackProcess<T2type>, T2type> || t2ProcSeq) {
         if (B.CheckStep()) { ret |= B.DoStack(vS); }
       }
       return ret;
@@ -152,64 +157,58 @@ namespace corsika::process {
           max_length = // if no other process in the sequence implements it
           std::numeric_limits<double>::infinity() * corsika::units::si::meter;
 
-      if constexpr (std::is_base_of<ContinuousProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<ContinuousProcess<T1type>, T1type> || t1ProcSeq) {
         corsika::units::si::LengthType const len = A.MaxStepLength(vP, vTrack);
         max_length = std::min(max_length, len);
       }
-      if constexpr (std::is_base_of<ContinuousProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<ContinuousProcess<T2type>, T2type> || t2ProcSeq) {
         corsika::units::si::LengthType const len = B.MaxStepLength(vP, vTrack);
         max_length = std::min(max_length, len);
       }
       return max_length;
     }
 
-    template <typename TParticle, typename TTrack>
-    corsika::units::si::GrammageType GetTotalInteractionLength(TParticle& vP,
-                                                               TTrack& vT) {
-      return 1. / GetInverseInteractionLength(vP, vT);
+    template <typename TParticle>
+    corsika::units::si::GrammageType GetTotalInteractionLength(TParticle& vP) {
+      return 1. / GetInverseInteractionLength(vP);
     }
 
-    template <typename TParticle, typename TTrack>
+    template <typename TParticle>
     corsika::units::si::InverseGrammageType GetTotalInverseInteractionLength(
-        TParticle& vP, TTrack& vT) {
-      return GetInverseInteractionLength(vP, vT);
+        TParticle& vP) {
+      return GetInverseInteractionLength(vP);
     }
 
-    template <typename TParticle, typename TTrack>
-    corsika::units::si::InverseGrammageType GetInverseInteractionLength(TParticle& vP,
-                                                                        TTrack& vT) {
+    template <typename TParticle>
+    corsika::units::si::InverseGrammageType GetInverseInteractionLength(TParticle& vP) {
       using namespace corsika::units::si;
 
       InverseGrammageType tot = 0 * meter * meter / gram;
 
-      if constexpr (std::is_base_of<InteractionProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
-        tot += A.GetInverseInteractionLength(vP, vT);
+      if constexpr (std::is_base_of_v<InteractionProcess<T1type>, T1type> || t1ProcSeq) {
+        tot += A.GetInverseInteractionLength(vP);
       }
-      if constexpr (std::is_base_of<InteractionProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
-        tot += B.GetInverseInteractionLength(vP, vT);
+      if constexpr (std::is_base_of_v<InteractionProcess<T2type>, T2type> || t2ProcSeq) {
+        tot += B.GetInverseInteractionLength(vP);
       }
       return tot;
     }
 
-    template <typename TParticle, typename TSecondaries, typename TTrack>
+    template <typename TParticle, typename TSecondaries>
     EProcessReturn SelectInteraction(
-        TParticle& vP, TSecondaries& vS, TTrack& vT,
+        TParticle& vP, TSecondaries& vS,
         [[maybe_unused]] corsika::units::si::InverseGrammageType lambda_select,
         corsika::units::si::InverseGrammageType& lambda_inv_count) {
 
-      if constexpr (is_process_sequence<T1type>::value) {
+      if constexpr (t1ProcSeq) {
         // if A is a process sequence --> check inside
         const EProcessReturn ret =
-            A.SelectInteraction(vP, vS, vT, lambda_select, lambda_inv_count);
+            A.SelectInteraction(vP, vS, lambda_select, lambda_inv_count);
         // if A did succeed, stop routine
         if (ret != EProcessReturn::eOk) { return ret; }
-      } else if constexpr (std::is_base_of<InteractionProcess<T1type>, T1type>::value) {
+      } else if constexpr (std::is_base_of_v<InteractionProcess<T1type>, T1type>) {
         // if this is not a ContinuousProcess --> evaluate probability
-        lambda_inv_count += A.GetInverseInteractionLength(vP, vT);
+        lambda_inv_count += A.GetInverseInteractionLength(vP);
         // check if we should execute THIS process and then EXIT
         if (lambda_select < lambda_inv_count) {
           A.DoInteraction(vS);
@@ -217,15 +216,15 @@ namespace corsika::process {
         }
       } // end branch A
 
-      if constexpr (is_process_sequence<T2>::value) {
+      if constexpr (t2ProcSeq) {
         // if A is a process sequence --> check inside
         const EProcessReturn ret =
-            B.SelectInteraction(vP, vS, vT, lambda_select, lambda_inv_count);
+            B.SelectInteraction(vP, vS, lambda_select, lambda_inv_count);
         // if A did succeed, stop routine
         if (ret != EProcessReturn::eOk) { return ret; }
-      } else if constexpr (std::is_base_of<InteractionProcess<T2type>, T2type>::value) {
+      } else if constexpr (std::is_base_of_v<InteractionProcess<T2type>, T2type>) {
         // if this is not a ContinuousProcess --> evaluate probability
-        lambda_inv_count += B.GetInverseInteractionLength(vP, vT);
+        lambda_inv_count += B.GetInverseInteractionLength(vP);
         // check if we should execute THIS process and then EXIT
         if (lambda_select < lambda_inv_count) {
           B.DoInteraction(vS);
@@ -251,12 +250,10 @@ namespace corsika::process {
 
       corsika::units::si::InverseTimeType tot = 0 / second;
 
-      if constexpr (std::is_base_of<DecayProcess<T1type>, T1type>::value ||
-                    is_process_sequence<T1>::value) {
+      if constexpr (std::is_base_of_v<DecayProcess<T1type>, T1type> || t1ProcSeq) {
         tot += A.GetInverseLifetime(p);
       }
-      if constexpr (std::is_base_of<DecayProcess<T2type>, T2type>::value ||
-                    is_process_sequence<T2>::value) {
+      if constexpr (std::is_base_of_v<DecayProcess<T2type>, T2type> || t2ProcSeq) {
         tot += B.GetInverseLifetime(p);
       }
       return tot;
@@ -268,12 +265,12 @@ namespace corsika::process {
         TParticle& vP, TSecondaries& vS,
         [[maybe_unused]] corsika::units::si::InverseTimeType decay_select,
         corsika::units::si::InverseTimeType& decay_inv_count) {
-      if constexpr (is_process_sequence<T1>::value) {
+      if constexpr (t1ProcSeq) {
         // if A is a process sequence --> check inside
         const EProcessReturn ret = A.SelectDecay(vP, vS, decay_select, decay_inv_count);
         // if A did succeed, stop routine
         if (ret != EProcessReturn::eOk) { return ret; }
-      } else if constexpr (std::is_base_of<DecayProcess<T1type>, T1type>::value) {
+      } else if constexpr (std::is_base_of_v<DecayProcess<T1type>, T1type>) {
         // if this is not a ContinuousProcess --> evaluate probability
         decay_inv_count += A.GetInverseLifetime(vP);
         // check if we should execute THIS process and then EXIT
@@ -284,12 +281,12 @@ namespace corsika::process {
         }
       } // end branch A
 
-      if constexpr (is_process_sequence<T2>::value) {
+      if constexpr (t2ProcSeq) {
         // if A is a process sequence --> check inside
         const EProcessReturn ret = B.SelectDecay(vP, vS, decay_select, decay_inv_count);
         // if A did succeed, stop routine
         if (ret != EProcessReturn::eOk) { return ret; }
-      } else if constexpr (std::is_base_of<DecayProcess<T2type>, T2type>::value) {
+      } else if constexpr (std::is_base_of_v<DecayProcess<T2type>, T2type>) {
         // if this is not a ContinuousProcess --> evaluate probability
         decay_inv_count += B.GetInverseLifetime(vP);
         // check if we should execute THIS process and then EXIT
@@ -322,9 +319,7 @@ namespace corsika::process {
 
   /// marker to identify objectas ProcessSequence
   template <typename A, typename B>
-  struct is_process_sequence<corsika::process::ProcessSequence<A, B> > {
-    static const bool value = true;
-  };
+  struct is_process_sequence<corsika::process::ProcessSequence<A, B>> : std::true_type {};
 
 } // namespace corsika::process
 
diff --git a/Framework/ProcessSequence/testProcessSequence.cc b/Framework/ProcessSequence/testProcessSequence.cc
index aa78ee89c4c012eb2df3d322b6b1ddf6fa44ba1e..e8bfe7c1c835762e64ccb3afed48962775dc24ae 100644
--- a/Framework/ProcessSequence/testProcessSequence.cc
+++ b/Framework/ProcessSequence/testProcessSequence.cc
@@ -100,8 +100,8 @@ public:
     cout << "Process2::DoInteraction" << endl;
     return EProcessReturn::eOk;
   }
-  template <typename Particle, typename Track>
-  GrammageType GetInteractionLength(Particle&, Track&) const {
+  template <typename Particle>
+  GrammageType GetInteractionLength(Particle&) const {
     cout << "Process2::GetInteractionLength" << endl;
     return 3_g / (1_cm * 1_cm);
   }
@@ -123,8 +123,8 @@ public:
     cout << "Process3::DoInteraction" << endl;
     return EProcessReturn::eOk;
   }
-  template <typename Particle, typename Track>
-  GrammageType GetInteractionLength(Particle&, Track&) const {
+  template <typename Particle>
+  GrammageType GetInteractionLength(Particle&) const {
     cout << "Process3::GetInteractionLength" << endl;
     return 1_g / (1_cm * 1_cm);
   }
@@ -220,12 +220,11 @@ TEST_CASE("Process Sequence", "[Process Sequence]") {
     Process3 m3(2);
 
     DummyData particle;
-    DummyTrajectory track;
 
     auto sequence2 = cp1 << m2 << m3;
-    GrammageType const tot = sequence2.GetTotalInteractionLength(particle, track);
+    GrammageType const tot = sequence2.GetTotalInteractionLength(particle);
     InverseGrammageType const tot_inv =
-        sequence2.GetTotalInverseInteractionLength(particle, track);
+        sequence2.GetTotalInverseInteractionLength(particle);
     cout << "lambda_tot=" << tot << "; lambda_tot_inv=" << tot_inv << endl;
   }
 
diff --git a/Processes/CMakeLists.txt b/Processes/CMakeLists.txt
index 2835a7043cc80101ef22d1301af981b5735de6bb..6afe1cc51acdc689b97a90dec334d727b61c7f60 100644
--- a/Processes/CMakeLists.txt
+++ b/Processes/CMakeLists.txt
@@ -10,6 +10,7 @@ add_subdirectory (TrackingLine)
 add_subdirectory (HadronicElasticModel)
 add_subdirectory (EnergyLoss)
 add_subdirectory (UrQMD)
+add_subdirectory (SwitchProcess)
 
 #add_custom_target(CORSIKAprocesses)
 add_library (CORSIKAprocesses INTERFACE)
diff --git a/Processes/HadronicElasticModel/HadronicElasticModel.cc b/Processes/HadronicElasticModel/HadronicElasticModel.cc
index 33f162e41531bf4008f91b21bb98e8afc13a7abb..9e05c521320787b1f8a42ca3c154cfa708285769 100644
--- a/Processes/HadronicElasticModel/HadronicElasticModel.cc
+++ b/Processes/HadronicElasticModel/HadronicElasticModel.cc
@@ -18,14 +18,12 @@
 #include <corsika/utl/COMBoost.h>
 
 #include <corsika/setup/SetupStack.h>
-#include <corsika/setup/SetupTrajectory.h>
 
 #include <iomanip>
 #include <iostream>
 
 using namespace corsika::setup;
-using Particle = corsika::setup::Stack::ParticleType;
-using Track = corsika::setup::Trajectory;
+using SetupParticle = corsika::setup::Stack::ParticleType;
 
 namespace corsika::process::HadronicElasticModel {
 
@@ -38,7 +36,7 @@ namespace corsika::process::HadronicElasticModel {
 
   template <>
   units::si::GrammageType HadronicElasticInteraction::GetInteractionLength(
-      Particle const& p, Track&) {
+      SetupParticle const& p) {
     using namespace units::si;
     if (p.GetPID() == particles::Code::Proton) {
       auto const* currentNode = p.GetNode();
@@ -79,7 +77,7 @@ namespace corsika::process::HadronicElasticModel {
   }
 
   template <>
-  process::EProcessReturn HadronicElasticInteraction::DoInteraction(Particle& p) {
+  process::EProcessReturn HadronicElasticInteraction::DoInteraction(SetupParticle& p) {
     if (p.GetPID() != particles::Code::Proton) { return process::EProcessReturn::eOk; }
 
     using namespace units::si;
diff --git a/Processes/HadronicElasticModel/HadronicElasticModel.h b/Processes/HadronicElasticModel/HadronicElasticModel.h
index 4180c04c514d00089fd044ab39027b9128a853ff..b3fd15fd2cdc6feac967182cff342b60f30e954d 100644
--- a/Processes/HadronicElasticModel/HadronicElasticModel.h
+++ b/Processes/HadronicElasticModel/HadronicElasticModel.h
@@ -56,8 +56,8 @@ namespace corsika::process::HadronicElasticModel {
         units::si::CrossSectionType y = 0.05608 * units::si::barn);
     void Init();
 
-    template <typename Particle, typename Track>
-    corsika::units::si::GrammageType GetInteractionLength(Particle const& p, Track&);
+    template <typename Particle>
+    corsika::units::si::GrammageType GetInteractionLength(Particle const& p);
 
     template <typename Particle>
     corsika::process::EProcessReturn DoInteraction(Particle&);
diff --git a/Processes/Pythia/Interaction.cc b/Processes/Pythia/Interaction.cc
index 6cdf54973a2d553a79f6b6ebcd97b4d5ecf6cf24..2a0cce386edc6dfc5a14f0f6fb84fd94aa5a85a7 100644
--- a/Processes/Pythia/Interaction.cc
+++ b/Processes/Pythia/Interaction.cc
@@ -15,7 +15,6 @@
 #include <corsika/environment/NuclearComposition.h>
 #include <corsika/geometry/FourVector.h>
 #include <corsika/setup/SetupStack.h>
-#include <corsika/setup/SetupTrajectory.h>
 #include <corsika/utl/COMBoost.h>
 
 #include <tuple>
@@ -28,7 +27,6 @@ using namespace corsika;
 using namespace corsika::setup;
 using Projectile = corsika::setup::StackView::ParticleType;
 using Particle = corsika::setup::Stack::ParticleType;
-using Track = Trajectory;
 
 namespace corsika::process::pythia {
 
@@ -168,7 +166,7 @@ namespace corsika::process::pythia {
   }
 
   template <>
-  units::si::GrammageType Interaction::GetInteractionLength(Particle& p, Track&) {
+  units::si::GrammageType Interaction::GetInteractionLength(Particle& p) {
 
     using namespace units;
     using namespace units::si;
diff --git a/Processes/Pythia/Interaction.h b/Processes/Pythia/Interaction.h
index ac27825acf0561d0d9e7e8e8b66961bdfc674e2f..3594358e0b39f528991183b4c414e8edaa3b5828 100644
--- a/Processes/Pythia/Interaction.h
+++ b/Processes/Pythia/Interaction.h
@@ -51,16 +51,16 @@ namespace corsika::process::pythia {
                     const corsika::particles::Code TargetId,
                     const corsika::units::si::HEPEnergyType CoMenergy);
 
-    template <typename TParticle, typename TTrack>
-    corsika::units::si::GrammageType GetInteractionLength(TParticle&, TTrack&);
+    template <typename TParticle>
+    corsika::units::si::GrammageType GetInteractionLength(TParticle&);
 
     /**
        In this function PYTHIA is called to produce one event. The
        event is copied (and boosted) into the shower lab frame.
      */
 
-    template <typename TProjctile>
-    corsika::process::EProcessReturn DoInteraction(TProjctile&);
+    template <typename TProjectile>
+    corsika::process::EProcessReturn DoInteraction(TProjectile&);
 
   private:
     corsika::random::RNG& fRNG =
diff --git a/Processes/Pythia/testPythia.cc b/Processes/Pythia/testPythia.cc
index 3fb2df13ecd1c24e674997a3c3aa468164f21d06..f6f09b84c17f80f8b579d1a11eba843e6ddbc964 100644
--- a/Processes/Pythia/testPythia.cc
+++ b/Processes/Pythia/testPythia.cc
@@ -118,14 +118,6 @@ TEST_CASE("pythia process") {
   auto const* nodePtr = theMedium.get(); // save the medium for later use before moving it
   universe.AddChild(std::move(theMedium));
 
-  geometry::Point const origin(cs, {0_m, 0_m, 0_m});
-  geometry::Vector<units::si::SpeedType::dimension_type> v(cs, 0_m / second, 0_m / second,
-                                                           1_m / second);
-  geometry::Line line(origin, v);
-  geometry::Trajectory<geometry::Line> track(line, 10_s);
-
-  random::RNGManager::GetInstance().RegisterRandomStream("s_rndm");
-
   SECTION("pythia decay") {
 
     setup::Stack stack;
@@ -173,7 +165,6 @@ TEST_CASE("pythia process") {
     process::pythia::Interaction model;
     model.Init();
     [[maybe_unused]] const process::EProcessReturn ret = model.DoInteraction(projectile);
-    [[maybe_unused]] const GrammageType length =
-        model.GetInteractionLength(particle, track);
+    [[maybe_unused]] const GrammageType length = model.GetInteractionLength(particle);
   }
 }
diff --git a/Processes/Sibyll/Interaction.cc b/Processes/Sibyll/Interaction.cc
index b15d9e8859e86d6426f6b78b7834fe2211f191f1..c089ec083c9c7d9ec1d91136cb0c7796dc958c57 100644
--- a/Processes/Sibyll/Interaction.cc
+++ b/Processes/Sibyll/Interaction.cc
@@ -118,8 +118,8 @@ namespace corsika::process::sibyll {
   }
 
   template <>
-  units::si::GrammageType Interaction::GetInteractionLength(SetupParticle& vP,
-                                                            Track&) const {
+  units::si::GrammageType Interaction::GetInteractionLength(
+      SetupParticle const& vP) const {
 
     using namespace units;
     using namespace units::si;
diff --git a/Processes/Sibyll/Interaction.h b/Processes/Sibyll/Interaction.h
index e7d7a0902116c2fceb9240cf9266d04a2ea2fd72..643bd0d51bd4f387aafa3870f2dddfb0ed1fe9d5 100644
--- a/Processes/Sibyll/Interaction.h
+++ b/Processes/Sibyll/Interaction.h
@@ -52,8 +52,8 @@ namespace corsika::process::sibyll {
     GetCrossSection(const corsika::particles::Code, const corsika::particles::Code,
                     const corsika::units::si::HEPEnergyType) const;
 
-    template <typename TParticle, typename TTrack>
-    corsika::units::si::GrammageType GetInteractionLength(TParticle&, TTrack&) const;
+    template <typename TParticle>
+    corsika::units::si::GrammageType GetInteractionLength(TParticle const&) const;
 
     /**
        In this function SIBYLL is called to produce one event. The
diff --git a/Processes/Sibyll/NuclearInteraction.cc b/Processes/Sibyll/NuclearInteraction.cc
index 31abd9da350e1c80c24868eb2313e860b51bd821..907e95b271bb44cfb4d2982f0f1f40f88cbb0eca 100644
--- a/Processes/Sibyll/NuclearInteraction.cc
+++ b/Processes/Sibyll/NuclearInteraction.cc
@@ -217,7 +217,7 @@ namespace corsika::process::sibyll {
   template <>
   template <>
   units::si::GrammageType NuclearInteraction<SetupEnvironment>::GetInteractionLength(
-      Particle& vP, Track&) {
+      Particle& vP) {
 
     using namespace units;
     using namespace units::si;
diff --git a/Processes/Sibyll/NuclearInteraction.h b/Processes/Sibyll/NuclearInteraction.h
index 6bee9ba7a7964e74112c2bf60e5cbd4b1c23c2fa..261f931321ed98119ab02f4e3cace952308fdbb7 100644
--- a/Processes/Sibyll/NuclearInteraction.h
+++ b/Processes/Sibyll/NuclearInteraction.h
@@ -53,11 +53,11 @@ namespace corsika::process::sibyll {
     std::tuple<corsika::units::si::CrossSectionType, corsika::units::si::CrossSectionType>
     GetCrossSection(Particle& p, const corsika::particles::Code TargetId);
 
-    template <typename Particle, typename Track>
-    corsika::units::si::GrammageType GetInteractionLength(Particle&, Track&);
+    template <typename Particle>
+    corsika::units::si::GrammageType GetInteractionLength(Particle&);
 
-    template <typename Projectle>
-    corsika::process::EProcessReturn DoInteraction(Projectle&);
+    template <typename Projectile>
+    corsika::process::EProcessReturn DoInteraction(Projectile&);
 
   private:
     TEnvironment const& fEnvironment;
diff --git a/Processes/Sibyll/testSibyll.cc b/Processes/Sibyll/testSibyll.cc
index d5f5d9bc8e39ac775de3fb9d541a18b596941bad..0c42c90abb86a758c45f5ad4a79ebe87d3f1d3fa 100644
--- a/Processes/Sibyll/testSibyll.cc
+++ b/Processes/Sibyll/testSibyll.cc
@@ -98,12 +98,6 @@ TEST_CASE("SibyllInterface", "[processes]") {
 
   const geometry::CoordinateSystem& cs = env.GetCoordinateSystem();
 
-  geometry::Point const origin(cs, {0_m, 0_m, 0_m});
-  geometry::Vector<units::si::SpeedType::dimension_type> v(cs, 0_m / second, 0_m / second,
-                                                           1_m / second);
-  geometry::Line line(origin, v);
-  geometry::Trajectory<geometry::Line> track(line, 10_s);
-
   random::RNGManager::GetInstance().RegisterRandomStream("s_rndm");
 
   SECTION("InteractionInterface") {
@@ -126,8 +120,7 @@ TEST_CASE("SibyllInterface", "[processes]") {
 
     model.Init();
     [[maybe_unused]] const process::EProcessReturn ret = model.DoInteraction(projectile);
-    [[maybe_unused]] const GrammageType length =
-        model.GetInteractionLength(particle, track);
+    [[maybe_unused]] const GrammageType length = model.GetInteractionLength(particle);
   }
 
   SECTION("NuclearInteractionInterface") {
@@ -153,8 +146,7 @@ TEST_CASE("SibyllInterface", "[processes]") {
 
     model.Init();
     [[maybe_unused]] const process::EProcessReturn ret = model.DoInteraction(projectile);
-    [[maybe_unused]] const GrammageType length =
-        model.GetInteractionLength(particle, track);
+    [[maybe_unused]] const GrammageType length = model.GetInteractionLength(particle);
   }
 
   SECTION("DecayInterface") {
diff --git a/Processes/SwitchProcess/CMakeLists.txt b/Processes/SwitchProcess/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..feac9f360ced5356d90ecd87cc7d4ca51939e0f6
--- /dev/null
+++ b/Processes/SwitchProcess/CMakeLists.txt
@@ -0,0 +1,50 @@
+set (
+  MODEL_HEADERS
+  SwitchProcess.h
+  )
+
+set (
+  MODEL_NAMESPACE
+  corsika/process/switch_process
+  )
+
+add_library (ProcessSwitch INTERFACE)
+CORSIKA_COPY_HEADERS_TO_NAMESPACE (ProcessSwitch ${MODEL_NAMESPACE} ${MODEL_HEADERS})
+
+set_target_properties (
+  ProcessStackInspector
+  PROPERTIES
+  VERSION ${PROJECT_VERSION}
+  SOVERSION 1
+#  PUBLIC_HEADER "${MODEL_HEADERS}"
+  )
+
+# target dependencies on other libraries (also the header onlys)
+target_link_libraries (
+  ProcessSwitch
+  INTERFACE
+  CORSIKAunits
+  CORSIKAprocesssequence
+  )
+
+target_include_directories (
+  ProcessSwitch 
+  INTERFACE 
+  $<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>
+  $<INSTALL_INTERFACE:include/include>
+  )
+
+install (FILES ${MODEL_HEADERS} DESTINATION include/${MODEL_NAMESPACE})
+
+# --------------------
+# code unit testing
+add_executable (testSwitchProcess testSwitchProcess.cc)
+
+target_link_libraries (
+  testSwitchProcess
+  ProcessSwitch
+  CORSIKAstackinterface
+  CORSIKAthirdparty # for catch2
+)
+
+CORSIKA_ADD_TEST(testSwitchProcess)
diff --git a/Processes/SwitchProcess/SwitchProcess.h b/Processes/SwitchProcess/SwitchProcess.h
new file mode 100644
index 0000000000000000000000000000000000000000..31e59599bc6dceb68edf4ad030d284eb37c69bce
--- /dev/null
+++ b/Processes/SwitchProcess/SwitchProcess.h
@@ -0,0 +1,98 @@
+#ifndef _corsika_SwitchProcess_h
+#define _corsika_SwitchProcess_h
+
+#include <corsika/process/InteractionProcess.h>
+#include <corsika/process/ProcessSequence.h>
+#include <corsika/setup/SetupStack.h>
+#include <corsika/units/PhysicalUnits.h>
+
+namespace corsika::process::switch_process {
+
+  /**
+   * This process provides an energy-based switch between two interaction processes P1 and
+   * P1. For energies below the threshold, P1 is invoked, otherwise P2. Both can be either
+   * single interaction processes or multiple ones combined in a ProcessSequence. A
+   * SwitchProcess itself will always be regarded as a ProcessSequence rather than an
+   * InteractionProcess when assembled into a greater ProcessSequence.
+   */
+
+  template <class TLowEProcess, class THighEProcess>
+  class SwitchProcess : public BaseProcess<SwitchProcess<TLowEProcess, THighEProcess>> {
+    TLowEProcess& fLowEProcess;
+    THighEProcess& fHighEProcess;
+    units::si::HEPEnergyType const fThresholdEnergy;
+
+  public:
+    SwitchProcess(TLowEProcess& vLowEProcess, THighEProcess& vHighEProcess,
+                  units::si::HEPEnergyType vThresholdEnergy)
+        : fLowEProcess(vLowEProcess)
+        , fHighEProcess(vHighEProcess)
+        , fThresholdEnergy(vThresholdEnergy) {}
+
+    void Init() {
+      fLowEProcess.Init();
+      fHighEProcess.Init();
+    }
+
+    template <typename TParticle>
+    corsika::units::si::InverseGrammageType GetInverseInteractionLength(TParticle& p) {
+      return 1 / GetInteractionLength(p);
+    }
+
+    template <typename TParticle>
+    units::si::GrammageType GetInteractionLength(TParticle& vParticle) {
+      if (vParticle.GetEnergy() < fThresholdEnergy) {
+        if constexpr (is_process_sequence_v<TLowEProcess>) {
+          return fLowEProcess.GetTotalInteractionLength(vParticle);
+        } else {
+          return fLowEProcess.GetInteractionLength(vParticle);
+        }
+      } else {
+        if constexpr (is_process_sequence_v<THighEProcess>) {
+          return fHighEProcess.GetTotalInteractionLength(vParticle);
+        } else {
+          return fHighEProcess.GetInteractionLength(vParticle);
+        }
+      }
+    }
+
+    // required to conform to ProcessSequence interface. We cannot just
+    // implement DoInteraction() because we want to call SelectInteraction
+    // in case a member process is a ProcessSequence.
+    template <typename TParticle, typename TSecondaries>
+    EProcessReturn SelectInteraction(
+        TParticle& vP, TSecondaries& vS,
+        [[maybe_unused]] corsika::units::si::InverseGrammageType lambda_select,
+        corsika::units::si::InverseGrammageType& lambda_inv_count) {
+      if (vP.GetEnergy() < fThresholdEnergy) {
+        if constexpr (is_process_sequence_v<TLowEProcess>) {
+          return fLowEProcess.SelectInteraction(vP, vS, lambda_select, lambda_inv_count);
+        } else {
+          lambda_inv_count += fLowEProcess.GetInverseInteractionLength(vP);
+          // check if we should execute THIS process and then EXIT
+          if (lambda_select < lambda_inv_count) {
+            fLowEProcess.DoInteraction(vS);
+            return EProcessReturn::eInteracted;
+          } else {
+            return EProcessReturn::eOk;
+          }
+        }
+      } else {
+        if constexpr (is_process_sequence_v<THighEProcess>) {
+          return fHighEProcess.SelectInteraction(vP, vS, lambda_select, lambda_inv_count);
+        } else {
+          lambda_inv_count += fHighEProcess.GetInverseInteractionLength(vP);
+          // check if we should execute THIS process and then EXIT
+          if (lambda_select < lambda_inv_count) {
+            fHighEProcess.DoInteraction(vS);
+            return EProcessReturn::eInteracted;
+          } else {
+            return EProcessReturn::eOk;
+          }
+        }
+      }
+    }
+  };
+} // namespace corsika::process::switch_process
+
+#endif
diff --git a/Processes/SwitchProcess/testSwitchProcess.cc b/Processes/SwitchProcess/testSwitchProcess.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4e902e8857367bfbb4d1ab7643941cdcce27c04c
--- /dev/null
+++ b/Processes/SwitchProcess/testSwitchProcess.cc
@@ -0,0 +1,256 @@
+#include <corsika/process/switch_process/SwitchProcess.h>
+#include <corsika/stack/SecondaryView.h>
+#include <corsika/stack/Stack.h>
+#include <corsika/units/PhysicalUnits.h>
+
+#define CATCH_CONFIG_MAIN // This tells Catch to provide a main() - only do this in one
+                          // cpp file
+#include <catch2/catch.hpp>
+
+#include <algorithm>
+#include <random>
+
+using namespace corsika;
+using namespace corsika::process;
+using namespace corsika::units::si;
+
+class TestStackData {
+
+public:
+  // these functions are needed for the Stack interface
+  void Init() {}
+  void Clear() { fData.clear(); }
+  unsigned int GetSize() const { return fData.size(); }
+  unsigned int GetCapacity() const { return fData.size(); }
+  void Copy(int i1, int i2) { fData[i2] = fData[i1]; }
+  void Swap(int i1, int i2) { std::swap(fData[i1], fData[i2]); }
+
+  // custom data access function
+  void SetData(unsigned int i, HEPEnergyType v) { fData[i] = v; }
+  HEPEnergyType GetData(const unsigned int i) const { return fData[i]; }
+
+  // these functions are also needed by the Stack interface
+  void IncrementSize() { fData.resize(fData.size() + 1); }
+  void DecrementSize() {
+    if (fData.size() > 0) { fData.pop_back(); }
+  }
+
+  // custom private data section
+private:
+  std::vector<HEPEnergyType> fData;
+};
+
+/**
+ * From static_cast of a StackIterator over entries in the
+ * TestStackData class you get and object of type
+ * TestParticleInterface defined here
+ *
+ * It provides Get/Set methods to read and write data to the "Data"
+ * storage of TestStackData obtained via
+ * "StackIteratorInterface::GetStackData()", given the index of the
+ * iterator "StackIteratorInterface::GetIndex()"
+ *
+ */
+template <typename StackIteratorInterface>
+class TestParticleInterface
+    : public corsika::stack::ParticleBase<StackIteratorInterface> {
+
+public:
+  using corsika::stack::ParticleBase<StackIteratorInterface>::GetStackData;
+  using corsika::stack::ParticleBase<StackIteratorInterface>::GetIndex;
+
+  /*
+     The SetParticleData methods are called for creating new entries
+     on the stack. You can specifiy various parametric versions to
+     perform this task:
+  */
+
+  // default version for particle-creation from input data
+  void SetParticleData(const std::tuple<HEPEnergyType> v) { SetEnergy(std::get<0>(v)); }
+  void SetParticleData(TestParticleInterface<StackIteratorInterface>& /*parent*/,
+                       std::tuple<HEPEnergyType> v) {
+    SetEnergy(std::get<0>(v));
+  }
+
+  // here are the fundamental methods for access to TestStackData data
+  void SetEnergy(HEPEnergyType v) { GetStackData().SetData(GetIndex(), v); }
+  HEPEnergyType GetEnergy() const { return GetStackData().GetData(GetIndex()); }
+};
+
+using SimpleStack = corsika::stack::Stack<TestStackData, TestParticleInterface>;
+
+// see issue 161
+#if defined(__clang__)
+using StackTestView = corsika::stack::SecondaryView<TestStackData, TestParticleInterface>;
+#elif defined(__GNUC__) || defined(__GNUG__)
+using StackTestView = corsika::stack::MakeView<SimpleStack>::type;
+#endif
+
+auto constexpr kgMSq = 1_kg / (1_m * 1_m);
+
+template <int N>
+struct DummyProcess : InteractionProcess<DummyProcess<N>> {
+  void Init() {}
+
+  template <typename TParticle>
+  corsika::units::si::GrammageType GetInteractionLength(TParticle const&) const {
+    return N * kgMSq;
+  }
+
+  template <typename TSecondaries>
+  corsika::process::EProcessReturn DoInteraction(TSecondaries& vSec) {
+    // to figure out which process was selected in the end, we produce N
+    // secondaries for DummyProcess<N>
+
+    for (int i = 0; i < N; ++i) {
+      vSec.AddSecondary(std::tuple<HEPEnergyType>{vSec.GetEnergy() / N});
+    }
+
+    return EProcessReturn::eOk;
+  }
+};
+
+using DummyLowEnergyProcess = DummyProcess<1>;
+using DummyHighEnergyProcess = DummyProcess<2>;
+using DummyAdditionalProcess = DummyProcess<3>;
+
+TEST_CASE("SwitchProcess from InteractionProcess") {
+  DummyLowEnergyProcess low;
+  DummyHighEnergyProcess high;
+  DummyAdditionalProcess proc;
+
+  switch_process::SwitchProcess switchProcess(low, high, 1_TeV);
+  auto seq = switchProcess << proc;
+
+  SimpleStack stack;
+
+  SECTION("low energy") {
+    stack.AddParticle(std::tuple<HEPEnergyType>{0.5_TeV});
+    auto p = stack.GetNextParticle();
+
+    // low energy process returns 1 kg/m²
+    SECTION("interaction length") {
+      REQUIRE(switchProcess.GetInteractionLength(p) / kgMSq == Approx(1));
+      REQUIRE(seq.GetTotalInteractionLength(p) / kgMSq == Approx(3. / 4));
+    }
+
+    // low energy process creates 1 secondary
+    //~ SECTION("SelectInteraction") {
+    //~ typename SimpleStack::ParticleType theParticle =
+    //~ stack.GetNextParticle(); // as in corsika::Cascade
+    //~ StackTestView view(theParticle);
+    //~ auto projectile = view.GetProjectile();
+
+    //~ InverseGrammageType invLambda = 0 / kgMSq;
+    //~ switchProcess.SelectInteraction(p, projectile, 0.01 / kgMSq, invLambda);
+
+    //~ REQUIRE(view.GetSize() == 1);
+    //~ }
+  }
+
+  SECTION("high energy") {
+    stack.AddParticle(std::tuple<HEPEnergyType>{4_TeV});
+    auto p = stack.GetNextParticle();
+
+    // high energy process returns 2 kg/m²
+    SECTION("interaction length") {
+      REQUIRE(switchProcess.GetInteractionLength(p) / kgMSq == Approx(2));
+      REQUIRE(seq.GetTotalInteractionLength(p) / kgMSq == Approx(6. / 5));
+    }
+
+    // high energy process creates 2 secondaries
+    SECTION("SelectInteraction") {
+    typename SimpleStack::ParticleType theParticle =
+    stack.GetNextParticle(); // as in corsika::Cascade
+    StackTestView view(theParticle);
+    auto projectile = view.GetProjectile();
+
+    InverseGrammageType invLambda = 0 / kgMSq;
+    switchProcess.SelectInteraction(p, projectile, 0.01 / kgMSq, invLambda);
+
+    REQUIRE(view.GetSize() == 2);
+    }
+  }
+}
+
+TEST_CASE("SwitchProcess from ProcessSequence") {
+  DummyProcess<1> innerA;
+  DummyProcess<2> innerB;
+  DummyProcess<3> outer;
+  DummyProcess<4> additional;
+
+  auto seq = innerA << innerB;
+
+  switch_process::SwitchProcess switchProcess(seq, outer, 1_TeV);
+  auto completeSeq = switchProcess << additional;
+
+  SimpleStack stack;
+
+  SECTION("low energy") {
+    stack.AddParticle(std::tuple<HEPEnergyType>{0.5_TeV});
+    auto p = stack.GetNextParticle();
+
+    SECTION("interaction length") {
+      REQUIRE(switchProcess.GetInteractionLength(p) / kgMSq == Approx(2. / 3));
+      REQUIRE(completeSeq.GetTotalInteractionLength(p) / kgMSq == Approx(4. / 7));
+    }
+
+    SECTION("SelectInteraction") {
+    std::vector<int> numberOfSecondaries;
+
+    for (int i = 0; i < 1000; ++i) {
+    typename SimpleStack::ParticleType theParticle =
+    stack.GetNextParticle(); // as in corsika::Cascade
+    StackTestView view(theParticle);
+    auto projectile = view.GetProjectile();
+
+    double r = i / 1000.;
+    InverseGrammageType invLambda = r * 7./4 / kgMSq;
+
+    InverseGrammageType accumulator = 0 / kgMSq;
+    completeSeq.SelectInteraction(p, projectile, invLambda, accumulator);
+
+    numberOfSecondaries.push_back(view.GetSize());
+    }
+
+    auto const mean =
+    std::accumulate(numberOfSecondaries.cbegin(), numberOfSecondaries.cend(), 0.) /
+    numberOfSecondaries.size();
+    REQUIRE(mean == Approx(12./7.).margin(0.01));
+    }
+  }
+
+  SECTION("high energy") {
+    stack.AddParticle(std::tuple<HEPEnergyType>{3.0_TeV});
+    auto p = stack.GetNextParticle();
+
+    SECTION("interaction length") {
+      REQUIRE(switchProcess.GetInteractionLength(p) / kgMSq == Approx(3));
+      REQUIRE(completeSeq.GetTotalInteractionLength(p) / kgMSq == Approx(12. / 7.));
+    }
+
+    SECTION("SelectInteraction") {
+      std::vector<int> numberOfSecondaries;
+
+      for (int i = 0; i < 1000; ++i) {
+        typename SimpleStack::ParticleType theParticle =
+            stack.GetNextParticle(); // as in corsika::Cascade
+        StackTestView view(theParticle);
+        auto projectile = view.GetProjectile();
+
+        double r = i / 1000.;
+        InverseGrammageType invLambda = r * 7. / 12. / kgMSq;
+
+        InverseGrammageType accumulator = 0 / kgMSq;
+        completeSeq.SelectInteraction(p, projectile, invLambda, accumulator);
+
+        numberOfSecondaries.push_back(view.GetSize());
+      }
+
+      auto const mean =
+          std::accumulate(numberOfSecondaries.cbegin(), numberOfSecondaries.cend(), 0.) /
+          numberOfSecondaries.size();
+      REQUIRE(mean == Approx(24. / 7.).margin(0.01));
+    }
+  }
+}
diff --git a/Processes/UrQMD/UrQMD.cc b/Processes/UrQMD/UrQMD.cc
index df4456bfb965f398720e33aafd286ed56bbdb307..98f7a7385727d30836e7590bfb6bd54f8de4f542 100644
--- a/Processes/UrQMD/UrQMD.cc
+++ b/Processes/UrQMD/UrQMD.cc
@@ -2,9 +2,6 @@
 #include <corsika/geometry/Vector.h>
 #include <corsika/particles/ParticleProperties.h>
 #include <corsika/process/urqmd/UrQMD.h>
-#include <corsika/random/RNGManager.h>
-#include <corsika/setup/SetupStack.h>
-#include <corsika/setup/SetupTrajectory.h>
 #include <corsika/units/PhysicalUnits.h>
 
 #include <algorithm>
@@ -20,7 +17,6 @@ UrQMD::UrQMD() { iniurqmd_(); }
 using SetupStack = corsika::setup::Stack;
 using SetupParticle = corsika::setup::Stack::StackIterator;
 using SetupProjectile = corsika::setup::StackView::StackIterator;
-using SetupTrack = corsika::setup::Trajectory;
 
 template <typename TParticle> // need template here, as this is called both with
                               // SetupParticle as well as SetupProjectile
@@ -82,7 +78,7 @@ bool UrQMD::CanInteract(particles::Code vCode) const {
                    vCode) != std::cend(validProjectileCodes);
 }
 
-GrammageType UrQMD::GetInteractionLength(SetupParticle& vParticle, SetupTrack&) const {
+GrammageType UrQMD::GetInteractionLength(SetupParticle& vParticle) const {
   if (!CanInteract(vParticle.GetPID())) {
     // we could do the canInteract check in GetCrossSection, too but if
     // we do it here we have the advantage of avoiding the loop
diff --git a/Processes/UrQMD/UrQMD.h b/Processes/UrQMD/UrQMD.h
index 11c8a0eb9a14268f1729a2fbf23508bcf024bcb4..a77e6e843b38055bc96c470c79f2902fcfa58ce5 100644
--- a/Processes/UrQMD/UrQMD.h
+++ b/Processes/UrQMD/UrQMD.h
@@ -5,7 +5,6 @@
 #include <corsika/process/InteractionProcess.h>
 #include <corsika/random/RNGManager.h>
 #include <corsika/setup/SetupStack.h>
-#include <corsika/setup/SetupTrajectory.h>
 #include <corsika/units/PhysicalUnits.h>
 
 #include <array>
@@ -17,7 +16,7 @@ namespace corsika::process::UrQMD {
     UrQMD();
     void Init() {}
     corsika::units::si::GrammageType GetInteractionLength(
-        corsika::setup::Stack::StackIterator&, corsika::setup::Trajectory&) const;
+        corsika::setup::Stack::StackIterator&) const;
 
     template <typename TParticle>
     corsika::units::si::CrossSectionType GetCrossSection(TParticle const&,