Scenario 1. The driver of a vehicle braked all the way while driving up a hill, and then proceeded to accelerate all the way driving down the hill.
Scenario 2. The driver of a vehicle wanted to meet up with someone traveling in the same direction, with the same speed, but far ahead of him. So he started braking to reduce the distance between them. After a while, he started accelerating, to avoid overtaking his target.
Scenario 3. The driver of a vehicle arrived to his destination, braking as hard as possible, with loud creaking and rattling, but everyone around considered it perfectly normal. Some time later, the driver of a similar vehicle with similar cargo arrived to the same place, braking and halting very gently. Everyone around cursed him and he got nearly fired from his job. (mention of cargo removed as it proved to be disorienting)
What vehicles was I talking about?
Hint: nothing is meant figuratively. All three cases are quite normal for the respective vehicles, they don't merely depict exceptional conditions.
This is a very standard practice for a vehicle of this type, nothing unusual. It is a very common vehicle. If the drive is moving up a hill, it does not necessarily mean that the vehicle as a whole would decelerate by itself.
It was correctly guessed that it's a spacecraft in orbit.
Many people guessed train, but not why it is important for a very long train not to stop too gradually.