It would be so boring to just drive at full speed. There has to be another way to keep this game from becoming a has-been. Nitro. This temporary boost can help you knock down opponents, get special bonuses, and achieve super fast lap times. Each car has different nitro efficiency, some drain faster than another, while some just sip it like a Prius would with its gas. It is not a one-time only deal during a race, as you can perform tricks by being a wreckless driver. Here's the ways you can get nitro, in order from smallest amount to the largest.
City Havoc < Traffic Control < Near Miss < Traffic Down < Perfect Runs* < Barrel Rolls or Flat Spins < Knockdown (opponents) < Blue Nitro Bottle (replenishes 25%) < Yellow Nitro Bottle (replenishes 50%)
Ways that can Vary: Drifting (depends on radius and length of drift), Air time (more will obviously give you more nitro)
* = Perfect runs are granted after you are "untouched" (you don't tap a wall, wreck, or hit traffic) for 15 consecutive seconds.
If you choose to, you can choose to have the Nitro Starter booster. Find out more about it by clicking here.