THE BIG crackdown began last week, and to all who have been used, abused, misdelivered or totally ignored by illegal cabdrivers in this city, it was a satisfying sight. All across town and on out to National Airport, there were cheers from onlookers as officers from the Metropolitan, Park and Airport police departments swooped down on scofflaws at a series of checkpoints. They issued more than 100 tickets -- at the rate of $500 apiece -- and impounded more than 40 jalopies posing as real taxis. Among those leading the cheers were the honest, professional and fully licensed drivers who were checking through in a matter of seconds -- and who have been furious for years at the city's failure to help them weed their industry of those who were ruining it.

The police are doing the city an enormous service. By Friday, word of the crackdown is said to have caused some of the illegal drivers to get off the streets. This put a dent in the supply of cabs, but the missing cabs were not fit to be on the street anyway, and the drivers who observe the laws hardly deserve their unfair competition. As cabbie James Watkins put it, "These illegal drivers are knocking me out of money. And they overcharge customers, who end up giving me a hard time. These unlicensed people don't give a damn."

They didn't seem to. Many of those found without the proper licenses blamed their failure to observe the law on exams that they claim are too tough. The test could stand some alterations, but flunking is not a license for driving a cab anyhow. Chairman Arrington Dixon and those members of the new D.C. Taxicab Commission who want full-speed-ahead improvements in cab service deserve support against those on the commission who have started dredging for excuses to stall. The results so far have been good. The commission should keep on going.