@classmethod
def index_to_speed(cls, index):
    """
            Convert an index among allowed speeds to its corresponding speed
        :param index: the speed index []
        :return: the corresponding speed [m/s]
        """
    if cls.SPEED_COUNT > 1:
        return cls.SPEED_MIN + index * (cls.SPEED_MAX - cls.SPEED_MIN) / (cls
            .SPEED_COUNT - 1)
    else:
        return cls.SPEED_MIN
