Since using a phone while driving is not more dangerous than simply driving, the question is equivalent to asking if it is dangerous to drive while drunk.
It may be a bit surprising to learn that it is not dangerous to use a phone while driving, as there are many studies which claim to have found the opposite. Unfortunately, road safety is an area where a huge amount of research can be found which is of very low quality. While your first link is now broken, I can follow the UK one and that study is of a quality I would describe as laughably and appallingly poor. It has these problems:
- very low sample size - only 20 participants
- very restricted participant type - only experienced drivers
- no driving was tested - it was all in a simulator
- no risk or danger occurred - participants knew that there was no chance of harm to anyone
- no measure of risk was used - the measure was of irrelevant proxies: speed control, response time, ability to answer questions
- self reporting - drivers own opinions are considered worth reporting
- highly biased research - the researchers are obsessed with danger to the extent that the word "safer" does not appear in the report, with the comparison either being reversed (X is more dangerous than Y rather than Y is safer than X) or being expressed as "less dangerous"
For anyone who wants to read the study for themselves, it's at TRL547
When reading studies on driving, there are a few red flags which should make you disregard any study as probably worthless. One of the most common is the use of a bogus proxy, and the most common of these is reaction time. It is well known that older people have slower reaction times than younger people, yet it is also well known that young people are much worse drivers than older people (especially by insureance companies who stand to lose a lot of money if they get that wrong). Consequently, reaction time is such a bad proxy that its use immediately calls into question the competence of any study. Other bogus proxies are things which are irrelevant to safety - such as lane following precision, or vehicle following precision. These are not quite so bad in that they may indicate driving ability in some narrow circumstances (e.g. selecting racing drivers) but are irrelevant to safety.
Another red flag is driver's opinions. People are extremely bad at self-assessment and there are many notorious psychological effects in this area, so no study should even bother asking drivers their opinions except as a way of suggesting further research.
In road safety, the only things that count are:
- serious injuries
- minor injuries
- property damage
People's opinions do not count. People's subjective feelings of danger do not count. Proxies do not count unless there is strong evidence of strong correlation with one of the factors that do count and proper consideration has been taken of confounding variables.
Ok. So it's time to show evidence why phone use is safe while driving.
For this I cite Driving under the (Cellular) Influence (paywalled)
which seems to be quite strong. Here is the abstract:
We investigate the causal link between driver cell phone use and
crash rates by exploiting a natural experiment induced by the 9 pm
price discontinuity that characterizes a majority of recent cellular
plans. We first document a 7.2 percent jump in driver call
likelihood at the 9 pm threshold. Using a prior period as a
comparison, we next document no corresponding change in the relative
crash rate. Our estimates imply an upper bound in the crash risk
odds ratio of 3.0, which rejects the 4.3 asserted by Redelmeier and
Tibshirani (1997). Additional panel analyses of cell phone ownership
and cellular bans confirm our result.
Note that this compares actual crash numbers - not proxies, and phone
use is during real driving - not simulations. Possibly the strongest
part is that the drivers were completely unaware that they were being
studied, so their behaviour was completely natural.
In fact, the most surprising thing in that study is that no
correlation was found. Even if phone use is completely safe, I'd
expect studies to find it correlated with crashes. This is because of
driver attitudes - drivers vary between very careful and quite
reckless, and I would expect that, since people are so often told that
phone use is dangerous, the more careful drivers would be more likely
to refrain from using a phone while driving. Assuming that more
careful drivers are less likely to have crashes, this should result in
a non-causal correction between phone use and crashes.
Most driving research fails to take into account the most important
property of drivers - they learn. There is no doubt that experienced
drivers are safer than novices, yet when mobile phones started
appearing the research effectively tested novice use of phones while
driving. Even if that is more dangerous, there's no a priori reason to
assume that this is uniquely difficult and that drivers can never
learn to do it safely.