diff --git a/qc_openscenario/checks/data_type_checker/non_negative_transition_time_in_light_state_action.py b/qc_openscenario/checks/data_type_checker/non_negative_transition_time_in_light_state_action.py
index 7eb2f57..dce5958 100644
--- a/qc_openscenario/checks/data_type_checker/non_negative_transition_time_in_light_state_action.py
+++ b/qc_openscenario/checks/data_type_checker/non_negative_transition_time_in_light_state_action.py
@@ -87,7 +87,11 @@ def check_rule(checker_data: models.CheckerData) -> None:
 
             return
 
-        current_numeric_value = float(current_transition_time)
+        current_numeric_value = utils.to_float(current_transition_time)
+
+        if current_numeric_value is None:
+            continue
+
         has_issue = current_numeric_value < 0
 
         if has_issue:
diff --git a/qc_openscenario/checks/data_type_checker/positive_duration_in_phase.py b/qc_openscenario/checks/data_type_checker/positive_duration_in_phase.py
index c3aabaf..8fb66f8 100644
--- a/qc_openscenario/checks/data_type_checker/positive_duration_in_phase.py
+++ b/qc_openscenario/checks/data_type_checker/positive_duration_in_phase.py
@@ -74,7 +74,11 @@ def check_rule(checker_data: models.CheckerData) -> None:
 
             return
 
-        current_numeric_value = float(current_duration)
+        current_numeric_value = utils.to_float(current_duration)
+
+        if current_numeric_value is None:
+            continue
+
         has_issue = current_numeric_value < 0
 
         if has_issue:
diff --git a/qc_openscenario/checks/utils.py b/qc_openscenario/checks/utils.py
index f9ba550..1bdb6e1 100644
--- a/qc_openscenario/checks/utils.py
+++ b/qc_openscenario/checks/utils.py
@@ -10,6 +10,13 @@
 PARAMETER_PATTERN = re.compile(r"[$][A-Za-z_][A-Za-z0-9_]*")
 
 
+def to_float(s):
+    try:
+        return float(s)
+    except (ValueError, TypeError):
+        return None
+
+
 def get_root_without_default_namespace(path: str) -> etree._ElementTree:
     with open(path, "rb") as raw_file:
         xml_string = raw_file.read().decode()