diff --git a/include/crpropa/module/Observer.h b/include/crpropa/module/Observer.h
index adf7c8fc4..42234998e 100644
--- a/include/crpropa/module/Observer.h
+++ b/include/crpropa/module/Observer.h
@@ -281,6 +281,17 @@ class ObserverTimeEvolution: public ObserverFeature {
 	DetectionState checkDetection(Candidate *candidate) const;
 	std::string getDescription() const;
 };
+
+class ObserverTrajectoryLength: public ObserverFeature {
+private: 
+	double maxLength; 
+public: 
+	ObserverTrajectoryLength(double l);
+
+	DetectionState checkDetection(Candidate *candidate) const;
+};
+
+
 /** @} */
 
 }
diff --git a/src/module/Observer.cpp b/src/module/Observer.cpp
index c600dce50..3b464ed15 100644
--- a/src/module/Observer.cpp
+++ b/src/module/Observer.cpp
@@ -365,4 +365,17 @@ std::string ObserverSurface::getDescription() const {
 	return ss.str();
 }
 
+// ObserverTrajectoryLength ---------------------------------------------------
+
+ObserverTrajectoryLength::ObserverTrajectoryLength(double l) : maxLength(l) { }
+
+DetectionState ObserverTrajectoryLength::checkDetection(Candidate *cand) const {
+	double currentLength = cand -> getTrajectoryLength(); 
+
+	if (currentLength > maxLength) 
+		return DETECTED;
+	
+	cand -> limitNextStep(maxLength - currentLength); 
+	return NOTHING;
+}
 } // namespace crpropa