Adapt locomotive brake initialization to respect DP brake sync

Author: SteelFill

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/Brakes/MSTS/AirSinglePipe.cs

@@ -594,10 +594,38 @@ public override void Restore(BinaryReader inf)
 
         public override void Initialize(bool handbrakeOn, float maxPressurePSI, float fullServPressurePSI, bool immediateRelease)
         {
+            MSTSLocomotive loco = Car as MSTSLocomotive;
+
             BrakeLine1PressurePSI = Car.Train.EqualReservoirPressurePSIorInHg;
             BrakeLine2PressurePSI = Car.Train.BrakeLine2PressurePSI;
-            if (Car is MSTSLocomotive && Car.Train.LeadLocomotive is MSTSLocomotive lead)
-                lead.EngineBrakeController?.UpdateEngineBrakePressure(ref BrakeLine3PressurePSI, 1000);
+            // Initialize locomotive brakes
+            if (loco != null && Car.Train.LeadLocomotive is MSTSLocomotive lead)
+            {
+                bool brakeLine3Init = false;
+
+                if (loco == lead) // Always initialize loco brakes on lead loco
+                    brakeLine3Init = true;
+                else
+                {
+                    foreach (List<TrainCar> group in Car.Train.LocoGroups)
+                    {
+                        if (group.Contains(loco))
+                        {
+                            if (group.Contains(lead))
+                                brakeLine3Init = true; // Always initialize loco brakes on locos in same group as lead loco
+                            else if (loco.DPSyncIndependent && lead.DPSyncIndependent)
+                                brakeLine3Init = true; // Otherwise, only initialize loco brakes if synchronized by DP system
+
+                            break;
+                        }
+                    }
+                }
+
+                if (brakeLine3Init) // Sync loco brakes with lead brake system
+                    lead.EngineBrakeController?.UpdateEngineBrakePressure(ref BrakeLine3PressurePSI, 1000);
+                else // Release loco brakes
+                    BrakeLine3PressurePSI = 0.0f;
+            }
             if (maxPressurePSI > 0)
                 ControlResPressurePSI = maxPressurePSI;
 
@@ -623,7 +651,7 @@ public override void Initialize(bool handbrakeOn, float maxPressurePSI, float fu
             IsolationValve = ValveState.Release;
             HandbrakePercent = handbrakeOn & HandBrakePresent ? 100 : 0;
             SetRetainer(RetainerSetting.Exhaust);
-            if (Car is MSTSLocomotive loco) 
+            if (loco != null) 
                 loco.MainResPressurePSI = loco.MaxMainResPressurePSI;
 
             // Prevent initialization triggering emergency vent valves