New research suggests that a distracted driver may be more dangerous than an intoxicated one.

Researchers from the University of Kentucky found that distractions make driving under the influence of alcohol less safe -- even when under the legal alcohol limit. Their study examines the degree to which distractions influence the ability of intoxicated drivers to safely control their vehicles.

On average, 28 alcohol-related traffic deaths are reported per day in the United States. To reduce such incidences in the future, law makers are now considering lowering the current legal limit of 0.08 percent alcohol concentration in the blood even more to 0.05 percent. These laws, however, are based on the assumption that it is safe to drive while below the legal limit. They do not take into account how distractions can further influence an intoxicated driver's ability to keep a vehicle on the road.

"With continuing advancements in technology and the omnipresence of distractions while driving, it is becoming increasingly important to study the interaction between alcohol and distraction on driving," researcher Nicholas van Dyke pointed out.

For the study, van Dyke and Mark Filmore tested how safely 50 adult participants could maneuver a 5.9 mile drive through a typical urban area after having a drink. A driving simulator was used. They took note of how well the drivers continuously made small adjustments to the steering wheel to keep the simulator vehicle within a designated lane, to prevent it from crossing into another or from veering onto the edge of the road. During some of these six-minute tests, the drivers also had to respond to small red circles appearing on the windshield of the simulator.

When tested separately, alcohol and distractions both impaired the key aspects of driving performance, such as within-line deviations, steering rate and lane exceedance. The magnitude to which alcohol impaired safe driving was increased two-fold when a driver also had to deal with distractions. This was evident even at blood alcohol levels below the current legal limit for driving in the US.

"A clearer understanding of how common distractions impact intoxicated drivers, especially at blood alcohol concentrations that are currently legal for driving in the United States, is an important step to reducing traffic accidents and fatalities and improving overall traffic safety," Filmore said.

The findings are detailed in the journal Psychopharmacology.