(a) Whenever a motor vehicle is being operated on a highway or shoulder adjacent thereto during the times specified in section 684, the driver shall use a distribution of light, or composite beam, directed high enough and of sufficient intensity to reveal persons and vehicles at a safe distance in advance of the vehicle, subject to the following requirements and limitations:

    (b) Whenever the driver of a vehicle approaches an oncoming vehicle within 500 feet, such driver shall use a distribution of light or composite beam so aimed that the glaring rays are not projected into the eyes of the oncoming driver.

     The lowermost distribution of light, specified in section 699 paragraph (c), shall be deemed to avoid glare at all times regardless of road contour and loading.