diff --git a/src/Devices/AtcBombardier.cs b/src/Devices/AtcBombardier.cs
index f988743..f399635 100644
--- a/src/Devices/AtcBombardier.cs
+++ b/src/Devices/AtcBombardier.cs
@@ -58,25 +58,25 @@ namespace OpenbveFcmbTrainPlugin
         private TrackStates TrackState;
 
         /// <summary>The time needed by the ATC device to initialize, in seconds.</summary>
-        private double InitializationTime;
+        private readonly double InitializationTime;
 
         /// <summary>A counter to keep track of initialization time, in seconds.</summary>
         private double InitializationCounter;
 
         /// <summary>The blinking time for lamps, in milliseconds.</summary>
-        private double BlinkTime;
+        private readonly double BlinkTime;
 
         /// <summary>A counter to keep track of blink time, in milliseconds.</summary>
         private double BlinkCounter;
 
         /// <summary>The time after which YARD mode enters idle state and engages the service brake, in seconds.</summary>
-        private double YardIdleTime;
+        private readonly double YardIdleTime;
 
         /// <summary>A counter to keep track of YARD mode idle time, in seconds.</summary>
         private double YardIdleCounter;
 
         /// <summary>The maximum speed in YARD mode, in km/h.</summary>
-        private double YardMaximumSpeed;
+        private readonly double YardMaximumSpeed;
 
         /// <summary>Represents an ATC movement permission order.</summary>
         private class MovementPermission
diff --git a/src/Devices/AtcDimetronic.cs b/src/Devices/AtcDimetronic.cs
index 3f834f8..ae59c1d 100644
--- a/src/Devices/AtcDimetronic.cs
+++ b/src/Devices/AtcDimetronic.cs
@@ -50,7 +50,7 @@ namespace OpenbveFcmbTrainPlugin
         private TrackStates TrackState;
 
         /// <summary>The maximum speed in YARD mode, in km/h.</summary>
-        private double YardMaximumSpeed;
+        private readonly double YardMaximumSpeed;
 
         /// <summary>Represents an ATC speed code.</summary>
         private class SpeedCode
diff --git a/src/Devices/Deadman.cs b/src/Devices/Deadman.cs
index 13cb93a..5800cda 100644
--- a/src/Devices/Deadman.cs
+++ b/src/Devices/Deadman.cs
@@ -24,10 +24,10 @@ namespace OpenbveFcmbTrainPlugin
         private double Counter;
 
         /// <summary>The delay time until the service brake is applied, in seconds.</summary>
-        private double BrakeDelay = 5.0;
+        private readonly double BrakeDelay = 5.0;
 
         /// <summary>Whether the train must be completely stopped to release the brakes.</summary>
-        private bool FullReset;
+        private readonly bool FullReset;
 
         /// <summary>Creates an instance of the Deadman device.</summary>
         /// <param name="brakeDelay">The delay before the brakes are applied, in seconds.</param>