Informal:
* Picking up speed: This is a very common and informal way to say that something is going faster.
* Going faster: This is a simple and straightforward way to say it.
* Speeding up: This is another common way to say it.
* Getting a move on: This implies that someone is trying to move quickly.
* Hitting the gas: This is a more informal way to say "speeding up", and it's often used in a car context.
Formal:
* Accelerating: This is the most formal way to say "increasing speed."
* Increasing velocity: This is another formal way to say it.
* Gaining momentum: This implies that something is getting faster and faster.
You can also use descriptive phrases:
* Going like a rocket: This implies that something is moving very quickly.
* Flying by: This implies that something is moving quickly and effortlessly.
* Zipping along: This implies that something is moving quickly and smoothly.
The best way to say "increasing speed" will depend on the context of your situation.