def correct_acc_clutch_on(gear_count, acc, transmission):
    """
    Get the acceleration If clutch is on. Maximum acceleration is
    decreased depending on the transmission.

    :param gear_count:
        Gear count.
    :type gear_count: int

    :param acc:
        Acceleration. (m/s2)
    :type acc:

    :param transmission:
        Transmission type.
    :type transmission: str

    :return:
        Acceleration when clutch on. (m/s2)
    :rtype:
    """
    if gear_count > 0:
        if transmission == 'manual':
            return 0.0
        else:
            return acc * 2 / 3
    else:
        return acc
