What is the significance of the railway tracks and the river at the of the novel in Ray Bradbury's Fahrenheit 451?

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.