A recent study conducted by 'Car and Driver' reveals that texting while driving is significantly more dangerous than driving while intoxicated. Drivers texting while operating a vehicle are 3-4 times slower than those driving drunk to apply brakes to avoid an accident.

Previous studies conducted in simulators have shown that texting can impair a driver's responses. 'Car and Driver' conducted this study in actual vehicles and directly compared reaction times of those texting with those driving under the influence. First the drivers performed the tests while sending text messages. Then they consumed enough alcohol to raise their blood alcohol content to .08%, the legal limit for intoxication in most states, and repeated the test with no cell phones.
In one set of results, a driver's response time while texting nearly tripled his baseline response. I think if you combine these results, with one national insurance provider's estimates that 20% of drivers regularly send text messages or emails while driving you have a very dangerous situation.