The Shodasamsa, also called the Kalamsa, is the sixteenth divisional chart: each sign is cut into sixteen parts of 1 degree 52 minutes 30 seconds, and the count starts from Aries for a movable sign, Leo for a fixed sign and Sagittarius for a dual sign. Brihat Parashara Hora Shastra ch. 6 assigns the D16 to vehicles, luxuries and material comforts.
Sixteen parts of 1 degree 52 minutes 30 seconds fill a sign. Unlike the divisions that start from the occupied sign, the D16 starts from a fixed sign chosen by modality: Aries if the planet is in a movable sign, Leo if in a fixed sign, Sagittarius if in a dual sign. From that start the sixteen parts run forward through the zodiac, wrapping once and continuing.
That fixed-start rule is shared exactly with the D45, which begins from the same three signs, and in a different form with the D20, which begins from Aries, Sagittarius and Leo. It has a practical consequence: two planets in different signs of the same modality can land in the same D16 sign, which does not happen in the divisions counted from the occupied sign.
The classical subject is vehicles, conveyances, luxuries and general material comfort, together with the happiness derived from them. The corresponding place in the birth chart is the 4th house, with Venus as the natural significator of vehicles and comforts, so a D16 reading is done beside those rather than on its own.
As with every varga, the division re-plots the same nine positions and cannot contradict the birth chart. It separates degrees that the sign-level chart groups together, which is the whole of what a division does; the promise stays where it was.
A shodasamsa is 1 degree 52 minutes 30 seconds wide, so the ascendant crosses one in about seven and a half minutes on average. A birth time known only to the nearest quarter hour is therefore not enough to fix the D16 lagna, though it is ample for the planets, since even the Moon takes about three and a half hours to change part.
AstroZivi names the subject BPHS gives the chart and reports the division exactly: each graha's sign, house from the D16 lagna, degree and dignity. It does not translate a placement into a statement about a vehicle or a purchase, because no reading it can cite makes that step.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.