several categories
There are more than two categories, however.
At times such as high-speed merge even listening to a passenger is too much distraction. The kind of time when you can't even afford the very brief time it takes to look at the speedo, for example. It all depends upon the driving conditions.
I group the various scenarios as follows:
1. no distraction - AT ALL
2. talk to passenger
3. tune radio
4. hands-free phone for short call
It turns out that talking to passengers does not significantly increase reaction times, but talking on the phone or texting, even when intermediated by a voice interface, does significantly increase reaction times. Therefore doing these things behind the wheel is a bad idea.
There are more than two categories, however.
At times such as high-speed merge even listening to a passenger is too much distraction. The kind of time when you can't even afford the very brief time it takes to look at the speedo, for example. It all depends upon the driving conditions.
I group the various scenarios as follows:
1. no distraction - AT ALL
2. talk to passenger
3. tune radio
4. hands-free phone for short call