The District estimated that it would issue 237,000 tickets a year from the street-sweeper cameras that would catch those parked during times when streets were supposed to be cleaned. It now appears that the real number will probably be 22,500, said Chief Financial Officer Natwar M. Gandhi. Gandhi revealed the shortfalls when he announced new revenue estimates for fiscal 2011 and 2012.

Meanwhile, cameras capturing drivers breaking speeding and other laws have generated much less revenue than expected: $8.5 million versus $20 million for a year ago, he said.

Mayor Vincent C. Gray (D) said that either the city overestimated or “maybe it is a better indication that people have been obeying the law.”