What words does the author use to avoid repeating "the road"?

One thing that Robert Frost does to avoid using the word "road" over and over again throughout this poem is to use pronouns instead of "road." For example, line five is as follows:

To where it bent in the undergrowth

"It" refers to one of the two roads. This pronoun is used again in line eight. In line ten, the narrator uses "them" instead of "roads."
For much of the rest of the poem, Frost substitutes various other words to stand-in for "road." The stand-in word is more often than not meant to be followed by the word "road," but Frost simply avoids using the word "road" and lets readers assume that the road is what he is talking about. For example, let's look at lines two and four:  

And sorry I could not travel both [roads]
And be one traveler, long I stood
And looked down one [road] as far as I could

Frost does this dropping of "road" a few more times in the poem. Lines six, eleven, and thirteen do the same thing.  
 
Finally, in line nineteen, the narrator substitutes "road" for the word "one."

I took the one less traveled by