In Ray Bradbury's Fahrenheit 451, the tracks and the river at the edge of the community symbolize not only change and hope, but also a new way of thinking.
In the novel, people have been encouraged to cease thinking on their own. Books are burned and those who read or collect books, are punished. Montag is a fireman who does this burning, but he is clearly not entirely dedicated to the sentiment of this brainwashed culture, as he has been hiding books. Clarisse, a new neighbor, notices things the rest of the desensitized society does not, including dew on the morning grass. She is a free-thinker, one who uplifts the value of original thought. Later when she is allegedly killed by a speeding car, the reader questions whether or not it was an accident.
However, as Montag listens to Clarisse, his value of reading and learning increase. Later, when Montag witnesses a woman who would rather burn with her books than leave them, he begins to actively question the wisdom of his leaders, searching out another man such as himself, Faber. With Faber he has the opportunity to discuss his changing ideas.
However, Montag's wife, Mildred, turns him in as a book owner, and Montag must burn his own house in the company of his boss, Beatty. Beatty, seemingly with a death wish, mentally and emotionally attacks Montag over and over, until Montag snaps, killing his boss.
Now a fugitive, Montag must cross the tracks, symbolic of taking the last literal step that will once and for all separate him from his oppressive society. The river will not only mask his scent from the avenging Hound, but will "baptize" Montag in his new beliefs, and carry him on to a place very unlike what he has known, so that he can grow with the knowledge of books, among other people who wish to read, learn and remember. It is from this new location that Montag and his new companions witness the total destruction of their society, even while hoping that they will one day be able to build a new community from this destruction—much like the mythical phoenix Montag's new acquaintance, Granger, notes:
There was a silly damn bird called a phoenix back before Christ, every few hundred years he built a pyre and burnt himself up...But every time he burnt himself up he sprang out of the ashes, he got himself born all over again. And it looks like we're doing the same thing, over and over...
The tracks and water represent the beginning of a new kind of life for Montag.