The trucks gain/gather 'speed' as they drive down the hill. = The trucks pick up 'speed' as they drive down the hill. [=the trucks go faster as they drive down the hill]
He types at a 'speed' of about 50 words per minute. = His typing 'speed' is about 50 words per minute.
Let me 'bring you up to speed' on our plans. [=let me tell you about the changes in our plans]
(..) Rocky, the ramp! Look out! Quick! Hold onto my tail! -Attaboy, Slink! -Oh! Woody! Woody! Speed up! -Speed up! -The batteries! They're runnin' out! -I can't hold on much longer. -Slink! Hang on! (..)1995 Toy Story