What literary techniques does Frost employ in "The Road Not Taken?"

The poem "The Road Not Taken" by Robert Frost is a narrative poem that uses the literary elements of first person narration, the story arc, symbolism, and analogy. The poem tells a story in the voice of its only character. The poem's story arc consists of the following:

Inciting incident: the narrator comes to a fork in the road.

Conflict: the narrator must decide which way to go.

Rising action: the narrator evaluates both paths.

Climax: the narrator decides: "Oh, I kept the first for another day!"

Falling action/denouement: narrator doubts if he will ever come back and reflects on his decision.

Theme: taking the route less traveled can impact one's life immensely.

The symbol (or metaphor) of the poem is the diverging path; it represents decision points in life. 

The symbol actually becomes an analogy, which is an extended metaphor with corresponding parts. The diverging paths represent a decision point, evaluating the pros and cons of each path is the decision-making process, and proceeding down one path is the choice a person makes which makes it unlikely that he or she "should ever come back." After a decision is made, there is often a "sigh" where one wonders if the correct action was chosen. Years later a person can look back and see how that one decision affected many things in his or her life.

By telling a simple story that is an analogy for the decision-making process we all are familiar with, Frost created a memorable and meaningful poem that has been touching the hearts of readers for 100 years.