"Initially considered too costly to install given projected ridership numbers, subway turnstiles are absent from Los Angeles subway stations. In fact, LA Metro is the only major transit agency in the U.S. that doesn't use subway turnstiles and security gates. This means that riders can, and do, waltz through stations without paying, undeterred by intermittent ticket checks and fines that run up to $250. As it turns out, more and more Angelenos are using the subway and those unpaid train tickets are adding up. Metro estimates that fare-evaders cost the system $5 million a year in lost revenue."
Critics have argued that the costs of installing the turnstiles outweigh the possible revenue increase, but no hard figures are available yet.