Stand on one leg. Touch your nose. Count backward. Are you high right now?

The latest push to develop a better, faster way to determine if drivers are high on cannabis is happening at UC San Diego in a $1.8-million study commissioned by the Legislature, and prompted by California's November vote on approving marijuana for legal recreational use.

While field sobriety tests are pretty good at determining if a driver is drunk, they're less reliable for potentially high motorists, whose impairment manifests itself in ways that are trickier to detect. Blood, saliva, and breath tests can all detect THC in the body, but fail to factor in either tolerance or duration since consumption. Plus, the results from the toxicology labs take weeks to arrive, gumming up the wheels of justice considerably even in legal states.

The drive to develop a roadside test

Hence the push from scientists, law enforcement, and researchers to develop a roadside test that not only detects cannabis in the driver's system, but the level of impairment they're experiencing.

Researchers in the UC San Diego study plan to use driving simulators to study people's behavior while they're high on marijuana. Using that data, they'll come up with new sobriety exercises that motorists would have to pass on an iPad or other handheld device.

"We want to be able to determine if a motorist is impaired by marijuana, how impaired they are and how long that impairment will last," Igor Grant, chair of psychiatry at the university and director of the Center for Medicinal Cannabis Research, told The San Diego Union Tribune.

"We also would like to measure the strength of the marijuana and how the potency relates to impairment," he added.

"People tend to experience distorted time and have problems with memory when stoned," said Barth Wilsey, a UC San Diego physician also involved in the study. "We aim to see whether these and other marijuana-related impairments might be detectable with tests on an iPad that could be used in the field by law-enforcement officers."