7.1.5 kilometers.

If this person drives a distance of $x$ from the moment they notice the bus, then the bus travels a distance of $3x$ during this time.

If this person drives towards the bus, and both arrive at the bus stop simultaneously, then $3x + x = 2$. Thus, this person drives 0.5 kilometers to the station. Therefore, if the distance to the station is greater than 0.5 kilometers, this person will not be able to reach the station in time.

If this person continues to drive in the original direction and arrives at the next station simultaneously with the bus, then $3x - x = 2$. Thus, this person drives 1 kilometer. Therefore, if the distance to the station exceeds 1 kilometer, this person will not be able to reach the station in time.
Therefore, the distance between stations should not exceed 1.5 kilometers.
7. A person wants to take a bus, but doesn't want to wait quietly at the bus stop. He rides a motorcycle from one bus stop to another, with his speed being $\frac{1}{3}$ of the bus's speed. When he sees the bus coming in his rearview mirror, he is 2 kilometers away from the bus. At this moment, he has two choices:
(1) Immediately turn around and head towards the bus to catch it at the next bus stop;
(2) Continue forward to the next bus stop to catch the bus.
What is the maximum distance between bus stops to ensure that this person will not miss the bus?