Citing estimates that 11 million people sometimes drive under the influence of illegal drugs, many in Congress want government action – but states are wary of the idea, The Associated Press reported.

Eight states now have drugged driving laws, but they are vague. That's partly because there's no roadside test to detect the presence of drugs in the body. And even if blood or urine samples taken at a hospital test positive for drugs, there's no standard for how high is too high to drive.

“Zero tolerance” is the level some lawmakers want Congress to establish. A motorist found to have any controlled substance in his or her system would be considered unlawfully impaired.

“Everyone who drives is affected by this,” Rep. Rob Portman, R-OH, said, citing a report last September by the Department of Health and Human Services estimating that during the previous year, nearly 11 million people drove at one time or another under the influence of drugs. The same survey said three times as many people – 33.5 million – drove under the influence of alcohol in 2002.

Under Portman's proposal, states that enact similar laws defining impaired as any detectible amount of drugs in a blood or urine sample would get money for training police and prosecutors and for driver counseling. They would also get grants to research field tests to measure motorists' drug levels.