Interesting facts that give insight to the answer to the question in the
subject line are at this Australian Mobile Telecommunications Association
site:
http://www.keepyoureyesontheroad.org...atistics-Cont#

This is a verbatim quote:
"If using mobile phones is significantly dangerous then we could expect to
see a dramatic increase in traffic accidents in the last decade. In fact,
the reverse is true."

The AMTA indicates that a tenth of 1 percent of Australian crashes are
"related" to illegal cellphone use:
http://www.keepyoureyesontheroad.org...atistics-Cont#
"Between 1997 and 2011 there were around 50,000 crashes each year on NSW
roads and less than 0.1 per cent of all crashes were related to illegal
hand-held mobile phone use."

Two caveats:
- We need to know what they mean by "related", and,
- We need to explore what they mean by "illegal" cellphone use.

You'll note that they say about Australia the same things I've been saying
about the USA, which is:
"Almost all Australian drivers now own a mobile phone, but the road
fatality reduction has continued despite the exponential increase in mobile
phone ownership over the last two decades. "

They do point out an interesting quirk of the statistics, which I hadn't
thought about, but which makes sense at face value:
"the dramatic increase in use of mobiles also increases the chance of a
fatal crash occurring when a driver is using a mobile phone (both legally
or illegally) and this may or may not be a causal association."

There is one other interesting statistic:
"A recent analysis of 340 serious casualty crashes in Victoria and NSW
between 2000 and 2011, using data gleaned from forensic examination of
crash scenes and anonymous interviews with drivers has found that in 0.9
per cent of crashes the driver was *using* a mobile phone."

Caveat:
- Using a cellphone does not mean the accident was caused by using it!

They summarize the situation in Australia as:
http://www.keepyoureyesontheroad.org...tatistics-Cont
"While mobile phones are a real distraction in the car and their use can
result in serious accidents, real life accident data indicates that mobile
phone use does not contribute significantly to crashes or fatalities."