People wear face masks on the Subway in Manhattan in New York City, on Nov 29, 2021.Across the United States, public transportation systems are suffering staff crunches with numerous unfilled job openings as the country reopens and people start returning to work. In Houston, the city's Metro public transportation system has posted more than 70 job openings in the past month. It is offering generous incentives to attract new bus drivers and mechanics. In St. Louis, a shortage of 150 perso...