Two Los Angeles traffic engineers have pleaded guilty to hacking into the city's traffic control computer, creating gridlock at four busy intersections, reports vnunet.com.

Prosecutors say Gabriel Murillo, 39, and Kartik Patel, 36, took the action as part of a union dispute over wages. The intersections they chose were near freeways, causing massive backups. It also took four days to get the computer system back to normal, according to the Los Angeles Times.

Murillo's attorney argued the matter should have been handled administratively. The men must pay full restitution, serve 120 days in jail or complete 240 hours of community service. In addition, their home and work computer use will be monitored.