In 2009, 78.5% of Dallas (city) commuters drive to work alone. The 2009 modal share for Dallas (city) commuters are 10.7% for carpooling, 3.9% for transit, 1.9% for walking, and .1% for cycling. In 2015, the American Community Survey estimated modal shares for Dallas (city) commuters of 75.4% for driving alone, 12.8% for carpooling, 3.5% for riding transit, 1.9% for walking, and .2% for cycling. The city of Dallas has a higher than average percentage of households without a car. In 2015, 10.2 percent of Dallas households lacked a car, and decreased to 9.1 percent in 2016. The national average was 8.7 percent in 2016. Dallas averaged 1.59 cars per household in 2016, compared to a national average of 1.8.

Answer this question based on the article: How many percent of Dallas commuters didn't drive to work alone in 2009?
21.5