It, unlike the earlier State Landaus, is postilion-driven.
From the en.wikipedia.org
The wagons had no driver's seat, so a postilion sat on the left rear horse and held his whip in his right hand.
From the en.wikipedia.org
There are historical exceptions, such as postilion riders in France, but such historical advantages do not apply to modern road vehicles.
From the en.wikipedia.org
As well as being slightly plainer in ornamentation, the Semi-state Landaus are distinguished from the State Landaus in that they are postilion-driven, rather than driven from the box.
From the en.wikipedia.org
More examples
Someone who rides the near horse of a pair in order to guide the horses pulling a carriage (especially a carriage without a coachman)
A postilion (or postillion, occasionally Anglicized to "post-boy") rider was the driver of a horse-drawn coach or post chaise, mounted on one of the drawing horses. By contrast, a coachman would be mounted on the vehicle along with the passengers.
One who guides a horse-driven coach by riding on the left-hand lead horse.