Heat is a wanted level system featured in Driver: Parallel Lines. It is a system that alerts the both the player of the crimes they commit and corresponds to the level of resistance the player receives from Police.
Generally, heat is gained when committing crimes that would normally raise suspicion in real life, and as such reflects a realistic wanted level system. The feature is in both eras and works the same in both.
When the player commits a crime, an amount of heat is added to the wanted bars found on the mini map (for on-foot behavior) and speedometer (for vehicular behavior). Because both of these wanted bars are separate, crimes committed in vehicles do not account for crimes committed on foot unless the player is/was seen by police after the heat is gained, at which point, the progressive amount of heat will be transferred over to the on-foot behavior bar. In a similar manner, crimes committed on foot will be transferred to the vehicle bar if/when they are seen entering a vehicle.
Because of the way heat is obtained, if the player enters (or switches) a vehicle while out of sight, the wanted bar in vehicles will not be given heat, and the player is therefore less likely to be pursued by police. However, if the player still has on-foot heat, suspicion is still gained when driving near police, assuming no crimes are actively committed at this point, and the longer the player spends around the police, the quicker the vehicle bar is filled with suspicion. If the bar becomes full of suspicion, a full amount of heat is given to the car and will be transferred fully if they are to exit the vehicle when in sight.
Wielding a weapon on foot is considered a crime, but will only give the player suspicion, which will gradually rise. If the player wields a weapon while in a vehicle and in sight of cops, they are given heat instantly. Similarly, if the player points a weapon at a police officer, they are given instant heat, while aiming at pedestrians will give only suspicion.
While heat is given only when in sight, sometimes, the player may be randomly given an active "in pursuit" status, randomly increasing their heat. This often occurs when the player has previously lost a wanted level and is still committing crimes (particularly speeding) while out of both pursuit and sight. This is likely a bug, given the random instance, however it may be pedestrians reporting the crime. Pedestrians report weapon and assault crimes committed the player when no police are nearby; firing a weapon, killing a pedestrian with their body of weapon, and attacking vehicles with weapons will result in 2 nearby police vehicles to respond to the scene of the crime. If the player moves ahead and commits one of the aforementioned crimes again, the police will move to the next crime scene, all in a short period of time. While this doesn't give the player heat, if the player remains at the crime scene, the player may sometimes be given heat, especially if they choose to follow the police vehicles when they head back to the police station. It must be noticed that police cars that drive away from the crime scene after inspecting for around 1 minute will simply drive erratically around the map for an indefinite amount of time and do not head to any particular location.
- Wreckless Driving (crashing or generally erratic driving): +2-3 bars*
- Hitting a pedestrian: +5-6 bars
- Resisting arrest: +1 bar (only accounts when bars are already attained)
- Possession of weapon: +3-4 bars (only accounts when bars are already attained) (will cause suspicion if welded when no active heat)*
- Shooting a pedestrian: +5-6 bars
- Shooting an office: +maxes bar out [ ]
- Speeding: +4-5 bars*
- * denotes inconsistent/irregular occurrences