@Override
                public ArithmeticMean<Double, Double> identity()
                {
                    return new ArithmeticMean<>();
                }

                @Override
                public ArithmeticMean<Double, Double> processSeries(final ArithmeticMean<Double, Double> intermediate,
                        final List<TrajectoryGroup<?>> trajectories, final List<Length> xFrom, final List<Length> xTo,
                        final Duration tFrom, final Duration tTo)
                {
                    for (int i = 0; i < trajectories.size(); i++)
                    {
                        TrajectoryGroup<?> trajectoryGroup = trajectories.get(i);
                        for (Trajectory<?> trajectory : trajectoryGroup.getTrajectories())
                        {
                            if (GraphUtil.considerTrajectory(trajectory, tFrom, tTo))
                            {
                                trajectory = trajectory.subSet(xFrom.get(i), xTo.get(i), tFrom, tTo);