How does a snail,
go across a road?
This poem is a question. The idea is for the reader to contemplate it.
A snail moves very slowly, and going across a road is hazardous. It would seem quite possible, that depending on the circumstances, that a snail might not complete the journey.
The chance of misfortune, though, is not the intent of the contemplation proposed by the poem. Instead, it is meant to motivate the reader, to consider how potentially unlikely success is achieved.
In some ways, the reader is prompted to consider the question “How did a snail, go across a road?” rather than how one could possible do so, given the difficulty.