Which Need for Speed game introduced street racing and car customization?

Need for Speed: Underground introduced the series’ defining combination of urban street racing and extensive car customization. Released in 2003, it moved the franchise away from scenic point-to-point sports-car races and into the tuner and import-car culture of a fictional Olympic City.

Players could modify both performance and appearance. Available upgrades included engines, tires, suspension, nitrous oxide, body kits, spoilers, paint, vinyls, underglow neon, exhausts, and wide-body parts. Underground also introduced Drag and Drift events, a story-driven career, and a Style Points system rewarding flashy driving.

Need for Speed: Underground 2, released in 2004, expanded those ideas with a larger free-roaming city and even more visual options. That sequel is therefore often named by mistake, but the original Underground was the game that first established the street-racing and customization formula.