Since the problem does not provide enough context to determine which initial distance is correct, we can only list the possible initial distances:
Without additional information, we cannot definitively choose one. However, if the problem intended to ask which distance would allow vehicle 1 to catch up to vehicle 2 in a specific time, more information would be needed.
Thus, the final answer is:
\[
\boxed{\text{Possible initial distances: 1000 m, 6000 m, 2000 m}}
\]