At least, that is what a natural experiment as a result of a three day Blackberry shutdown in two Arab states would suggest.
Of course, if this was accompanied by security measures in addition to a blackberry shutdown, the natural experiment may not be as clean as it seems. But, provisionally, at least, this seems to have been a purely technical breakdown,, which would support the natural experiment's conclusions.
Nobody doubts that handheld electronic devices can impair driving, and Colorado recently banned texting while driving. But, I don't think that many people would have expected the impact to be so great. Another key fact that may play a part is that the Islamic ban on alcohol, even if it isn't perfectly honored in practice, may significantly reduce the incidence of driving while intoxicated which makes up a very large percentage of U.S. accidents. The fact that not much traffic in these microstates involves long distance trips may also reduce the importance of another major U.S. accidents source: lack of sleep and extremely high speeds. The reduced importance of alcohol and sleep deprivation and extremely high speeds in accidents may elevate the importance of other potential risks, like distractions from electronic devices, proportionately.