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]
(..) What happened here? Judgment Day happened. I gotta get out of here. You can't go on foot. The machines will cut you down. You need speed. I need a car. Well, look, there's some by Griffith Observatory. -They don't run though. -Take me. (..)2009 Terminator Salvation