Carriages, and the way people drive them, are one of the main symbols of status employed in Northanger Abbey. James Morland, who is low on cash, has to rent a carriage while the wealthy Tilney's of course own very nice ones. John Thorpe makes an overt link between social status and carriages when he comments on James Morland:
"Morland is a fool for not keeping a horse and a gig of his own."
"No, he is not," said Catherine warmly, "for I am sure he could not afford it." (11.56-7)
People with less money are forced to rent shoddy carriages and horses here, which John finds annoying. Since John himself has little money and yet keeps his own horse and carriage, it is most likely that he is in some debt. Back in the day carriages were like your car – so James is driving around a beat up old station wagon, essentially. And John has blown all of his money on the equivalent of a snazzy new car.
Carriages, and how they are driven, also symbolize the character of some of the leading male figures in the book. Catherine even notes the contrast between her two suitors, John and Henry, based on their driving skills:
Henry drove so well, - so quietly - without making any disturbance, without parading to her, or swearing at them; so different from the only gentleman-coachman whom it was in her power to compare him with! (20.5)
Carriages, and how they are driven, comment on character's personalities as well as their respective class statuses.