Researchers at the University of Utah have published a study that claims drivers on cell phones are prone to more crashes than drunk drivers. Two psychology professors, David Strayer and Frank Drews, along with toxicology professor Dennis Crouch, conducted the study. 40 test subjects drove a simulated highway while undistracted, drunk and talking on a cellphone. The cell phone using drivers crashed three times, while the drunk drivers surprisingly did OK.
Researchers found that the drunk drivers were more aggressive and followed closer than the cell phone using drivers. They also discovered that cell phone users had significantly slower brake times at 849 ms versus 777 ms of the baseline group. Researchers suggest that cell phones make drivers more sluggish in perception and reaction.
Amazingly the drunk group's times did not significantly different from the baseline group. In addition, there were no crashes with the drunk group even though they had a tendancy to follow up to 2.5 meters (about 8 ft) closer than the cell phone group. The drunk group also had to brake much harder to avoid accidents.
The researchers simulated a 24-mile two-way highway on a "PatrolSim" driving simulator, commonly used by police officers for high-speed pursuit training. In 15-minute driving sessions, the test subjects had to follow and avoid hitting a pace car that would randomly brake. Passing vehicles were thrown is as distractions.
The volunteers had to do the same course four separate times. The first was a baseline test with no cellphone usage or alcohol consumption. Then handheld and hands-free cell phone usage were tested with the subjects maintaining a casual conversation with a research assistant. The final test was done after drinking a mixture of vodka and orange to get the subjects to a .08% blood alcohol level - the legal definition of driving while intoxicated in many states. Unfortunately, researchers didn't test drunk driving with cell phone usage.
There are two issues that can be raised about the study. The first is that crashing in a simulator does not have the same visceral and tragic consequences as crashing in real life. To be sure, there are some huge safety and legal problems with doing a live highway test, but perhaps the volunteers would have done better in a real environment.
Also, while .08% blood alcohol level is considered drunk, that level is usually on the low end for drunk drivers that have crashed. It's not uncommon to find drivers with double that level after an accident.
Full study from the Human Factors and Ergonomics Society