Pulmonía translates to pneumonia in English, a nickname that comes from the local belief that a ride in one of these open air cars will get you a cold, but the benevolent and warm climate of Mazatlán makes it hard to believe.
In fact, there is no better way to get around downtown and Zona Dorada for both locals and tourists, as they are surprisingly affordable and make for an good experience while getting around.

Their ubiquitous presence and importance when it comes to fast and cheap transport made them an icon of Mazatlán, just like Hummers are to Culiacán, to the point of having a dedicated sculpture at the seaside Malecon:

They started operating the 20th December 1965, substituting the old-fashioned carriages called arañas (spiders), with big wheels and horse-drawn. Their inventor, Miguel Ramírez Urquijo, imported 8 Cushman motors and their respective chassis from the USA, where they were used as mailsters, and later added their characteristic fiberglass structure and a fourth wheel.

Of course, they faced a huge backlash from the taxi cab driver’s syndicate, as they had the monopoly of the vehicles for hire (remember, unions in Mexico are basically mobsters), but their appearance and to gave them the upper hand.
Nowadays, it is impossible to say that you have been in Mazatlan without riding in one of them! The fares should be around 20 pesos for short rides, and besides that, your negotiation skills should come up in handy.