Sprinting/speed increase over time

I’m trying to create a movement system that allows the character to slowly accelerate towards a sprint, picking up speed along the way. After looking at the car system and flying system, I still can’t figure out how to slowly increase speed while forward is held and then decelerate once released.

Any tips on how to accomplish this fading through speed states? I’m aiming to apply effects at certain speeds, so more along the lines of sprinting based on time rather than a button press. It’s for a large character that has a wind up to their speed, think giant robot.

I know how to blend through walking, to running, to sprint. But only through inputs for each

There is a node called Get Input Key Time Down.
You can use the time the button is held down, and increment the speed accordingly.

You may want to use a curve if you want to easy change the acceleration.