MANILA — In Alvin Ocampo’s 18-year-old jeepney, the dashboard is held together with yards of peeling electrical tape. The only concession to Manila’s stifling heat is a fan screwed to the ceiling. And unless you count the padlocked metal grate in place of the driver’s-side door that Mr. Ocampo installed after a gang of glue-sniffing teenagers robbed him of a fistful of pesos, the vehicle has no safety features to speak of.

Nevertheless, on a recent Friday afternoon in December, scores of passengers climbed aboard Mr. Ocampo’s jeepney, one of thousands of locally produced passenger trucks that are icons of Manila’s traffic-clogged and pollution-choked streets.

Sitting knee-to-knee, 20 passengers squeezed along the vinyl benches that run the length of the vehicle. Women clutched purses on their laps, and a few riders held handkerchiefs over their noses to keep from breathing the acrid air streaming through the open windows.

For decades, the jeepney, patterned after World War II-era American jeeps and painted in brash designs, has been the most widely used mode of transportation in the country, earning the nickname “king of the road.”