Usage patterns
〈物〉が高速で〈動詞〉for something to (move/operate) at high speed
The Shinkansen runs at high speed.
高速に乗るto get on the expressway
If we get on the expressway from here, we'll arrive quickly.
高速を降りるto get off the expressway
Let's get off the expressway at the next interchange.
高速が混んでいるthe expressway is congested
The expressway is very congested because of the long holiday.