Samuel I. Schwartz, a.k.a. Gridlock Sam, is an American transportation engineer, most notable for popularizing the phrase "gridlock". Educated at Brooklyn College (BS Physics) and the University of Pennsylvania (MSCE), he originally worked as a New York City cabbie. He served as NYC Traffic Commissioner from 1982 to 1986 and when the traffic department became subsumed by the Department of Transportation held the second-in-command post of First Deputy Commissioner and Chief Engineer from 1986-1990. He started his own firm, Sam Schwartz Consulting, LLC, in 1995. The firm, with a staff of over 100, has offices in seven cities: New York, Newark, Chicago, Los Angeles, Tampa, D.C. and Philadelphia.
Sam designed a trolley system in Aruba, engineered the transportation plan for the Barclays Center, and orchestrated construction activities at the World Trade Center site.
He writes columns for New York City's Daily News, lower Manhattan’s Downtown Express, The Queens Chronicle and in the Yiddish News Report as Gridlock Shmuel. He answers questions by mail and alerts readers about traffic and transit patterns. He also blogs for PBS and Engineering News-Record.