def speed(self):
        """Calculate speed between :class:`Points`.

        Returns:
            list of float: Speed between :class:`Point` elements in km/h
        """
        if not len(self) > 1:
            raise RuntimeError('More than one location is required')
        try:
            times = [i.time for i in self]
        except AttributeError:
            raise NotImplementedError('Not all Point objects include time '
                                      'attribute')

        return (distance / ((times[i + 1] - times[i]).seconds / 3600)
                for i, distance in enumerate(self.distance()))