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There have been numerous studies that show how using a phone while driving is more distracting than other non-driving tasks and even worse than driving while intoxicated.

Here was a study done in the US:

When controlling for driving difficulty and time on task, cell-phone drivers exhibited greater impairment than intoxicated drivers.

And one in the UK:

Drivers also reported that it was easier to drive drunk than to drive while using a phone. It is concluded that driving behaviour is impaired more during a phone conversation than by having a blood alcohol level at the UK legal limit (80mg / 100ml).

However, these are all studies where the researchers created situations analogous to driving in real traffic. Is there any naturalistic evidence that shows one way or the other that the tests done in controlled conditions translate into the real world?

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    What kind of evidence would you expect? – Sklivvz Jun 30 '14 at 2:39
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    "I would expect a strong correlation in accident rates with phone usage trending upwards over the past 20 years": But there are confounding factors galore. Many advances in auto safety have been made over the past 20 years (airbags, antilock brakes, traction control, etc), so even if phones tended to increase the accident rate, other factors might drive the rate down overall. Without cell phones, perhaps the rate would have decreased even more. – Nate Eldredge Jun 30 '14 at 2:59
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    I'd love a question on this topic, but this one is a bit confused right now. You ask in the title whether the claims made in studies are true, which makes it tough to answer, because obviously you don't accept such studies as sufficient evidence. Then you speculate that the number of car accidents should have gone up - but no-one else is making that claim. Perhaps they understand that there are too many confounding factors (better cars & roads, better training and other interventions, lower drink-driving rates, higher seat-belt wearing rates, lower car-ownership amongst youths, etc.) – Oddthinking Jun 30 '14 at 4:27
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    @Gabe: That's a simple fallacy, unless you first account for all the confounding factors. Without evidence, I would bet a lot of drivers only text significantly in stop-start traffic, which I'd predict leads to more rear-end taps, but not many more deaths. But that's just my speculation, so it is out of scope in a question. – Oddthinking Jun 30 '14 at 7:31
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    Driving itself is believed to be a dangerous activity. Yet as driving rates have dramatically increased over the past century life expectancy has actually increased. Explain – Richard Tingle Jun 30 '14 at 14:24
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tl;dr: No.

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:

  • deaths
  • 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.

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  • "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." Do you think, just perhaps, there might be other confounding factors that might explain this? Less driving experience, different risk taking profiles, more kms driven per day, cheaper cars... just as a start. – Oddthinking Feb 17 at 22:53
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    The main paper you cite is interesting, but I think you are leaning on it too hard. They report an upper confidence limit of the odds ratio of 3.0, so it is plausible to them that the risk of accidents increases. Table 1 undermines your argument that all other studies rely on proxies. They explicitly address the question comparing it to drunk driving, and I think you should quote that. – Oddthinking Feb 17 at 23:07
  • It should also be noted that they are discussing talking on the phone. Based on the adverts I have seen, authorities are more worried about texting. – Oddthinking Feb 17 at 23:08
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    @oddthinking - 1) There is no mention of texting in the question, so I have answered the question asked, not the one you imagined was asked. 2) I refer to reaction time as a bad proxy, so of course there are confounding factors - that's the whole point I am making - that reaction time is not a suitable thing to measure. 3) I do not rely on the cited study. I rely on the fact that the claim that using a phone while driving is significantly dangerous is itself fairly implausible and so needs very strong evidence, I only cite the study to show that even more evidence is required. – ch. Feb 18 at 2:09
  • 1) The question is about phone use. This study only looked at one aspect of phone use (phone calls) and didn't look at other aspects (including texting, maps and games). I strongly suspect phone calls are a minority use in by drivers in 2019 - so it doesn't address the complete question. My objection remains, despite your dismissal of it as imagined. – Oddthinking Feb 18 at 4:48

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