Do not join two independent clauses with a comma only; this error in punctuation is called a comma splice (or comma fault).
Aspen was too far to drive, we decided to fly. [comma splice]
A comma splice can be corrected in several ways. Choose the one that best expresses the relation between the clauses and that sounds the best in the paragraph. The first three methods of revision that follow are appropriate when the two clauses are of equal importance, and the fourth method is best when you want to emphasize one of the clauses.
1. Substitute a semicolon for the comma, or substitute a semicolon and a conjunctive adverb or a transitional word or phrase (for a list, see transitions). When a
conjunctive adverb connects two independent clauses, it must be preceded by a
semicolon and followed by a comma.
Aspen was too far to drive, /; we decided to fly.
OR
Aspen was too far to drive; therefore, we decided to fly. [conjunctive adverb]
• Add a coordinating conjunction following the comma. Aspen was too far to drive, so we decided to fly.
• Create two sentences. Be aware, however, that putting a period between two brief statements may result in two choppy sentences. (See choppy writing.)
Aspen was too far to drive. We decided to fly.
4. Subordinate one clause to the other. This method of revision is often the most
effective because it emphasizes the more important idea.
Because Aspen was too far to drive, we decided to fly
