Underground 2 is the first game in the series to feature an open world, where players can drive freely around and explore the city, unlocking areas by winning races. Racing modes are roughly similar to Underground; one racing mode was dropped, this being the Knockout competitions. A Lap Knockout option is available when racing Circuit in non-career races.
Circuit race is a standard race that involves up to four cars driving around a track that loops back to the start line of itself. A circuit race has typically a minimum of 2 laps to a maximum of 5 laps.
Sprint race is a point-to-point race involving a maximum of four vehicles.
Drifting is one of the technical aspects of Underground 2. On the "parkade" tracks, the player drifts with up to 3 other competitors at the same time on the parkade tracks. Points are awarded when the player successfully slides the car and finishes each drift without hitting any walls or traffic. No nitrous oxide is allowed. There are also downhill drift events where the player drifts the car while progressing down the course from top to bottom. In the downhill drifts, there are no other racers, but there is normal city traffic. Players increase their points by sliding past city cars.
Unlike Underground, time plays a crucial role here, especially in parkade tracks; if the opponents end up crossing the finish line way before the player, a 30-second timer will start within which the players will have to accumulate drift points until the timer runs out or they cross the finish line.
Drag racing is another technical aspect of the game; a straight-line race that forces players to use the manual transmission. Like Underground, steering in this mode is simplified to simply allow for lane changes, while the game handles the steering along the lanes. The HUD in this mode is enlarged and displayed on either side of the screen; emphasizing on monitoring them, especially the tachometer and the engine's temperature. The players' positions will get forfeited if they collide into traffic or barriers, or overheat their engine due to prolonged redlining.
Apart from these, four new race variations have also been provided in Underground 2:
Street X mode is similar to circuit races, except that they take place in closed and tight tracks. A maximum of 4 racers participates in this event. Like drift mode, this mode disables the use of nitrous oxide.
Underground Racing League (URL) is a set of tournaments that takes place in a specific set of closed tracks outside city streets - either actual racing circuits or airport runways. URL tournaments typically consist of one to three races, with up to six cars (both in career mode and online). In tournaments with two or more races, a points system is used. At the end of each race, drivers receive a specific number of points according to their standing in a race. The total score at the end of these races determines the winner of the tournament.
Special events - these are similar to sprints, intending to reach a target point on the map, which is a "photographer", and the player needs to reach the target within a specific time limit. Achieving this will reward the player with a magazine cover.
Outruns - while in free roam, the player can challenge specific opponent cars (an outrun opponent car will have bright tail lights, similar to the player's cars when they use nitrous oxide) in an "outrun", where the goal is to start an outrun and then distance their car from the opponent's car by 300 metres (1,000 feet). The player can choose when to initiate an outrun and can take any path and/or use tactics to achieve this goal, provided they are in the lead. Each stage, including stage 1, has a limited number of outruns a player can win. For example, in the intro stage where the player is driving Rachel's car, 3 outruns can be won. After winning the number of outruns allowed for a stage, the outrun opponent cars cease to appear. After completing a career, there is no limit to the number of outruns wins allowed. Depending on the stage, after winning some number of outruns, the player is rewarded with a unique part. Some stages allow a player to do a series of outrun sequences, rewarding the player with multiple unique parts (one for each series of outruns won). The outrun mode is similar to that of Tokyo Xtreme Racer and Wangan Midnight video games, which use health bars instead of distance to determine the winner.
The races are divided into 5 "stages". Once any stage is completed, the race locations of that stage will be replaced by the counterparts of the next stage. A "World Map" feature includes a menu of races for all prior stages, denoting races that have been completed and yet to be completed. After completing stage 2 through stage 5 (these stages require completing some number of "DVD" events), there will always be 8 sponsor races that will not be completed, since a player has to choose a single sponsor per stage and can only run 3 out of 11 unique sponsor races, leaving 8 sponsor races incomplete at the end of each stage. These can only be run using World Map. Due to a game bug (at least on the PC version), if running a non-completed race from the World Map, no credit (cash or rep) will be awarded unless the player restarts at least once after the race starts.
Underground 2 is unique in the Need for Speed series in the sense that it requires a player to drive to a certain place in the city to begin a race (other games allow the player to select a race from a menu). Most races are marked on the in-game radar, but some are hidden and the player must search for them, should they decide to play them. The following features aid the players in this regard:
Cell phone / SMS system - During gameplay, the players will occasionally receive phone calls or text messages. The game maintains a list of messages and game info that can be reviewed via a menu system.
Cash and info icons - Each stage, including the intro stage, includes a set of hovering icons scattered throughout the game world. As the player explores the map in free roam, the player receives a cash reward and/or info as the player discovers and drives through each of the icons.