A ticket for transportation at a reduced rate in consideration of some special circumstance, as increase of travel; specif., a ticket for a certain number of, or for daily, trips between neighboring places at a reduced rate, such as are commonly used by those doing business in a city and living in a suburb. Commutation tickets are excepted from the prohibition against special rates contained in the Interstate Commerce Act of Feb. 4, 1887 (24 Stat. 379), and in 145 U. S. 263 it was held that party tickets were also excepted as being “obviously within the commuting principle.”  [Webster 1913 Suppl.]