Percent of public transporation expenditures spent on selected modes of transporation, by income group, 1997 Airline Mass Ship Intercity transit train Lowest 20 percent 50.9 25.4 0.7 5.8 Second 20 percent 60.0 19.5 0.8 4.2 Third 20 percent 61.4 20.5 1.8 5.6 Fourth 20 percent 64.2 11.7 8.1 5.8 Highest 20 percent 70.0 9.9 6.0 5.5