THE UNION that represents Maryland state troopers is furious about an agreement between the American Civil Liberties Union and the Maryland State Police settling litigation over racial profiling in traffic stops. The state police brass did not admit fault, but they agreed to implement policies that, the union argues, tar troopers as racists for doing their jobs. In the face of significant statistical evidence that black motorists get stopped disproportionately often, the union's argument that no problem exists seems thin. But opponents of the new agreement have a point, for it does not require the one thing that could have the largest impact: immediately putting cameras on all troopers' cars.

The union's sense of insult aside, the changes the agreement mandates are fairly modest. Profiling is already against the rules in Maryland, and much of the agreement merely obligates the state police to abide by existing policies. Advocates for motorists who claim to have been stopped on account of their race welcome provisions requiring police to review data on traffic stops and to take early action to address any problems that emerge. They also praise the agreement's creation of a police-citizen board and changes to complaint procedures. These changes -- under which troopers will hand out brochures advising motorists they have stopped how to file complaints -- particularly upset the union. We sympathize with the union on the brochure issue; the data requirements strike us as useful. But the major problem with the changes is that they largely leave in place an environment in which subjective impressions can be all but impossible to mediate.

A stop that, to a cop, is a reasonable move based on a sound instinct can be seen by a motorist as unwarranted and racially motivated harassment. The challenge is to prevent police from acting out of prejudice without inhibiting reasonable judgments or making police too risk-averse. The best way to do this is by putting cameras on cruisers, as New Jersey has done. Cameras, in combination with well-articulated policies, give police the ability to demonstrate in retrospect their compliance with the rules or else show their behavior as beyond the pale. The state police have already put cameras on cars patrolling Interstate 95, but that's a small percentage of the force -- and the agreement says only that more cameras will be installed "when and to the extent that financing becomes available." Cameras are not cheap, but they would let troopers know that they are being watched and give them a chance, when accused, to explain themselves.