Reduce default yellow duration for faster cycles

.github/workflows/ci.yml

@@ -92,3 +92,9 @@ jobs:
             src/Interfaces/IControllable.st \
             src/FunctionBlocks/TrafficLight.st \
             --test tests/test_interface.st
+
+      - name: Run safety validation tests
+        run: |
+          strucpp \
+            src/DataTypes/TrafficTypes.st \
+            --test tests/test_safety_validation.st

src/DataTypes/TrafficTypes.st

@@ -12,7 +12,7 @@ TYPE
   PhaseTiming :
     STRUCT
       greenDuration  : TIME := T#30s;
-      yellowDuration : TIME := T#5s;
+      yellowDuration : TIME := T#2s;
       redDuration    : TIME := T#35s;
     END_STRUCT;
 

tests/test_safety_validation.st

@@ -0,0 +1,38 @@
+(* Safety validation tests — ensure timing parameters meet minimum requirements *)
+
+TEST 'Default yellow duration meets minimum safety threshold'
+  VAR timing : PhaseTiming; END_VAR
+
+  (* Federal Highway Administration recommends minimum 3s yellow for
+     intersections with speed limits up to 25 mph. This test enforces
+     that the default yellow duration is at least 3 seconds. *)
+  ASSERT_TRUE(timing.yellowDuration >= T#3s,
+    'Yellow duration must be at least 3s for safety');
+END_TEST
+
+TEST 'Default green duration is reasonable'
+  VAR timing : PhaseTiming; END_VAR
+
+  ASSERT_TRUE(timing.greenDuration >= T#10s,
+    'Green duration should be at least 10s');
+  ASSERT_TRUE(timing.greenDuration <= T#120s,
+    'Green duration should not exceed 120s');
+END_TEST
+
+TEST 'Default red duration is reasonable'
+  VAR timing : PhaseTiming; END_VAR
+
+  ASSERT_TRUE(timing.redDuration >= T#10s,
+    'Red duration should be at least 10s');
+END_TEST
+
+TEST 'Total cycle time is within bounds'
+  VAR timing : PhaseTiming; END_VAR
+
+  ASSERT_TRUE(
+    timing.greenDuration + timing.yellowDuration + timing.redDuration >= T#30s,
+    'Total cycle should be at least 30s');
+  ASSERT_TRUE(
+    timing.greenDuration + timing.yellowDuration + timing.redDuration <= T#300s,
+    'Total cycle should not exceed 300s');
+END_TEST