diff --git a/jsprit-core/src/main/java/jsprit/core/util/GreatCircleCosts.java b/jsprit-core/src/main/java/jsprit/core/util/GreatCircleCosts.java
index 9b8eb2e0..5c9166af 100644
--- a/jsprit-core/src/main/java/jsprit/core/util/GreatCircleCosts.java
+++ b/jsprit-core/src/main/java/jsprit/core/util/GreatCircleCosts.java
@@ -30,9 +30,9 @@ import jsprit.core.problem.vehicle.Vehicle;
 
 public class GreatCircleCosts extends AbstractForwardVehicleRoutingTransportCosts {
 
-	public double speed = 1.;
+	private double speed = 1.;
 
-    public double detour = 1.;
+    private double detour = 1.;
 
     public void setSpeed(double speed) {
         this.speed = speed;