Is talking and driving more dangerous than any other type of distraction?

Question

Are there any studies that demonstrate that talking on a cell phone is more dangerous than any other type of distraction? Yes, it seems clear that talking on a cell phone is a distraction, but for the number of laws passed, I would expect that it be demonstrated that it is more of a distraction (to deserve being singled out legally).

Other common distractions

• Radio
• Talking to passengers
• Intoxication
• Fatigue
• Eating/Drinking
• Reading (no, I'm not kidding, people do it)
• Applying makeup (also common)

Answer 1

Distraction of talking on a cell phone compared to:

• Talking to other passengers
  As for how talking on a cell phone relates to talking to other passengers, there's actually some research showing that the former is a greater distraction. See Passenger and cell-phone conversations in simulated driving (PDF!)

  From the results:

  drivers in the cell-phone condition were four times more likely to fail in finishing the task [successfully exiting at the correct highway exit] than drivers in the passenger condition

• Listening to radio
  From a general study on how language tasks interferes with visual tasks, a comparison is made between listening and talking, which seems relevant, as cell phone use employs both, while listening to the radio only requires the former:

  "We measured their attention level and found that subjects were four times more distracted while preparing to speak or speaking than when they were listening," said Almor of the 47 people who participated in the experiment. "People can tune in or out as needed when listening." ^{* Experimental Psychology via Newswise}

• Intoxication
  I haven't looked for any research in this area. I don't know of a country where driving intoxicated is legal. Comparing the exact blood concentration required to equate with the distraction of cell phone use would probably be a rather laborious endeavour.

• Eating/Drinking, Reading, Applying makeup
  These are all already illegal under the broader headline of reckless driving.

• Fatigue
  This is a tricky one, as it's quite hard to quantify. There would be several practical problems with enforcing a law here. Partially because it is hard to objectively measure how tired someone is, but from another point of view, it is easy to relay the responsibility of not reading, talking on a cell phone, being intoxicated, etc, to the driver. These are all distractions that the driver can easily avoid. It would be problematic, in comparison, to demand that all drivers avoid becoming tired.

  Having said that, if that was the only problem with fatigue, we would probably have considered it a minor one, and worked around it. There is policy regarding this to some extent, already: there are laws controlling how long a professional driver (such as a truck or cab driver) is allowed to work without rest, and (at least in Sweden) if you do fall asleep while driving, it will be considered in court that you've been driving recklessly. I'm guessing the practical issues with implementation are what's differentiating this item from driving under the influence, which is prohibited regardless of whether or not you actually cause an accident.