"Speed" typically refers to a class of stimulant drugs, particularly amphetamines, often used recreationally for their euphoric effects. Adderall, on the other hand, is a prescription medication that contains a mixture of amphetamine salts and is used to treat ADHD and narcolepsy. While both can increase alertness and energy, Adderall is formulated for medical use with specific dosages and a controlled release, whereas "speed" can vary widely in purity and potency and is illegal when not prescribed.

The movie "Speed," released in 1994, was rated R primarily for intense action sequences, violence, and strong language. The film features several scenes of destruction and peril, including explosions and gunfire, which contribute to its high-stakes tension. Additionally, the dialogue includes profanity, reflecting the characters' stress and urgency in life-threatening situations. These elements combined to warrant the R rating, indicating it may not be suitable for viewers under 17 without parental guidance.

In the context of the movie "Speed," speed refers to the rate at which an object moves or travels. More specifically, it highlights the urgency and danger of the plot, where a bus is rigged to explode if it slows down below 50 miles per hour. This concept of speed is central to the film's tension, emphasizing the need for quick thinking and action to save the passengers. In a broader sense, speed can denote not only physical velocity but also the intensity and pace of life, reflecting high-stakes situations.

Keanu Reeves declined to reprise his role in "Speed 2: Cruise Control" because he felt the sequel did not have a strong enough script or concept to match the original film's success. He expressed concerns that the story didn't capture the same intensity and excitement that made "Speed" popular. Reeves ultimately chose to focus on other projects that aligned better with his artistic vision, leading to Jason Patric taking over the lead role in the sequel.