Should I stop using my phone as a pedestrian?

I often listen to music or use my phone while walking through town. I have heard that this is dangerous and could cause me to get killed, so I’ll attempt a back of the envelope calculation to work out if I should stop.

Firstly, the base rate of risk for being run over as a pedestrian in the UK is 0.0006% per person each year. Let’s say as a young man I face double that risk, or 0.0012%. I don’t know how much using my phone some of the time while walking raises the risk, though this data suggests a pedestrian failing to look properly was the cause of 190 road fatalities in the UK, out of a total of 385 pedestrian deaths. For the sake of argument, let’s say the risk triples. Let me know if you have a better estimate. That would result in an extra risk of death of 0.0024% each year. Dying now would cost me some 60 years of healthy life, so I should expect to lose 0.00144 years for each year I engage in this behaviour – which is around 12 hours.

As compensation, I get to listen to music, audiobooks and check my email for on average 10 minutes a day, which comes to 60 hours or so a year. I would say that time is about 50% better spend than it would be otherwise thanks to my ability to use my phone, so I expect to gain the equivalent of 30 hours a year.

If these numbers are about right, I should be fairly comfortable listening to music or looking at my phone as a pedestrian. However, the harm is pretty close to the benefit, and someone could reasonably think the cost actually outweighs the benefit.

Nonetheless I could do better by not using my phone in cases where the cost exceeds the benefit, for example by keeping the volume low, not having conversations which are particularly distracting, and being strict about not starting to look at my phone if I expect to cross the street soon after.

If you like this approach – and maybe even if you don’t – you’ll also like How to Gain or Lose 30 Minutes of Life Every Day, which estimates how much life you should expect to gain or lose each time you exercise, eat fruit, vegetables or meat, drink alcohol, smoke a cigarette, remain overweight, or sit at a computer for hours at a time. Gains and losses are measured using the ‘micromort‘, which corresponds to half an hour of life. While the numbers are no doubt a dramatic simplification of the medical evidence, I find a concrete estimate of the benefits gives me stronger motivation to eat more vegetables, drink less, and perhaps exercise more as well. And it helps me prioritise which health enhancing activities are worth the trouble, and which are not.

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  • Joshua Kaye

    >That would result in an extra risk of death of 0.0024% each year. Dying now would cost me 60 years of healthy life, so I should expect to lose 0.00144 years each year of I engage in this behaviour – which is around 12 hours, or 24 ‘micromorts‘.

    I recommend as an antidote to this kind of thinking the preface to Nassim Taleb’s Fooled by Randomness.  There is no such thing as a micromort, only an actual mort. 

    I understand this is intended to be a way to force the brain to weigh risks that we tend to either overlook or overemphasize.  But it is better to develop strategies to minimize the (already low) risk of death from phone utilization, than to try to quantify away death.

    • robertwiblin

      Why would that be better?

      • Dave92F1

        Because death is a binary thing.  You don’t really lose  a little life expectancy each time you engage in that behavior – instead, you play Russian roulette, and win or lose (usually win).

        BTW, yes, you should stop using your phone as a pedestrian.  It’s not well suited to walking – it works much better for communicating.  :-)

      • Margin

        “You don’t really lose  a little life expectancy each time you engage in that behavior”

        Actually, you do.

        Life expectancy is the expected number of remaining life-years at a given age.

        With riskier behavior, this number goes down.

  • louisep

    But of course the harm isn’t limited just to dying, and not just to you. You might be injured rather than killed. If you are hit by a car, bicycle or other pedestrian somebody else might be injured (or killed) too.

    And there could be opportunity costs of not paying attention to your surroundings — you might miss seeing a friend across the street, or spotting the ideal birthday present for your impossible to buy for other half. But that should be taken account of in your 50% better estimate, I guess.

  • Margin

    “Dying now would cost me some 60 years of healthy life”

    Rob, what do you think about Black Swans such as:

    1) A global pandemic kills you or reduces your quality of life indirectly
    2) Antibiotics stop working and you gain a 3% p.a. probability of dieing from simple infection
    3) Political risks (totalitarianism) because of new surveillance and riot control tech
    4) The whole AGI nano bio terror etc. risks
    5) Nuclear war
    6) Persistent new pollutants
    7) Economic risks, resource scarcity
    etc.

    Do you think they’re all small or do you think they are compensated by positive Black Swans (e.g. better cancer treatments etc.)

    I intuitively see my life expectancy with less optimism than you do.

    • robertwiblin

      I also worry a lot about these things. But there are tail risks on the upside too, for example through radical life extension or cryonics. But that’s life/death. I don’t want to forecast the whole future to work out if I should use my phone!

  • Guy Srinivasan

    “As compensation, I get to listen to music, audiobooks and check my email for on average 10 minutes a day, which comes to 60 hours or so a year. I would say that time is about 50% better used that it would be otherwise thanks to my ability to use my phone, so I expect to gain the equivalent of 30 hours a year.”
    This doesn’t work. Your time while walking-without-a-phone is not the equivalent of your time while not walking, so by using that time 50% better you don’t gain 30 hours, you gain 30 walking-without-a-phone hours. You need a conversion from 1 walking-without-a-phone hour to 1 average hour to compare your gain of 30 walking-without-a-phone hours to your loss of 12 hours.

    • robertwiblin

      I meant 50% better used relative to an average hour.

  • IMASBA

    “Dying now would cost me some 60 years of healthy life, so I should expect to lose 0.00144 years each year I engage in this behaviour – which is around 12 hours, or 24 ‘micromorts‘.”
    The reason the risk is so low is because the car drivers watch the road while you don’t. You are really pissing them off when you are walking around without paying attention (don’t stress hormones shorten lives as well?). This should really be taken into account, as well as the all the costs to society that have to do with unattentive pedestrians getting hit by cars but surviving.

  • IMASBA

    P.S. when a pedestrian is hit the car driver faces an investigation that will screw up his life for months, sometimes even years and that’s assuming the investigators correctly conclude that it was the pedestrians fault.

    The biggest advantage of having a “no phone while on the road” policy is that it gives you back some private time. It’s very satisfying to tell your boss “can’t talk now, I’m on the road” and prohibits him from abusing modern technology to usurp your leisure time (it goes without saying that all the time you spend on the phone on work related stuff outside working hours won’t show up on your paycheck).

  • Robert Koslover

    Oh, c’mon.  When I read your description that “this is dangerous and could cause me to get killed,”my first thought was, “Huh? Are there packs of crazed killers in your town that are out stalking and murdering unsuspecting cell-phone users?”  Cuz, ya see, *that* kind of thing would certainly be worthy of concern!  But no — for the very next thing I learned was that you were merely concerned about being accidentally run over, while paying insufficient attention to the world around you.  Really, now!  Maybe you should just *watch where you are going*, huh?  Oh, and here’s another fantastic, valuable, super-healthful, and dramatically life-extending hint for you, yet offered to you free of charge: As you walk across busy urban  intersections, do NOT stare continuously upward at birds, clouds, and/or planes flying overhead, no matter how interesting they may appear!  This one simple hint can significantly increase your lifespan! Can you guess why?

    • Tyrrell McAllister

      Your advice is “watch where you are going”.  Instituting a policy of not using one’s phone is a practical, actionable way towards implementing your advice.  So why the sarcasm?

      • Robert Koslover

        I considered the sarcasm appropriate because the topic is evidently so trivial.  For example, would you consider it appropriate for Overcoming Bias to run a similar column weighing (with math!) the relative risks vs rewards of (among others) 1: tying one’s shoes prior to walking or simply leaving them untied to save time; (2) zipping one’s fly upon leaving the bathroom vs saving time by leaving it unzipped; (3) putting on a seatbelt when driving vs not bothering, so as to save time; (4) washing one’s hands before eating vs not-washing, and then working out the odds of catching a hand-carried disease vs the time and water consumed in washing, etc.  Oh heck, ya know, come to think of it, I guess that I must admit that I actually would NOT be surprised to see columns on some of those actual subjects at this blog!  So… never mind.  Sigh.

  • VV

     So you utility is just linear in your remaining life expectancy? No discounting? No risk aversion? No costs for survivable injury?

    It seems to me that this form of GIGO pseudo-rational calculus, a mind ritual where you multiply largely made up numbers, is a typical fallacy among the self-proclaimed aspiring rationalists that populate this board and Less Wrong.

    • robertwiblin

      That’s not my instinctive preference, but the one I think I should have on reflection. I should include survivable injury though.

      What is your alternative approach to making decisions like this other than guessing the costs and benefits and weighing them up?

      • Thomas_L_Holaday

        How about including the cost you impose on whoever hits your music-lovin’ ass?

      • Tyrrell McAllister

        Perhaps.  But it should be noted that that would amount to doing *more* of what VV was criticizing, not less.

      • VV

         Try to estimate probabilities. Try to get an intuitive grasp of these probabilities (this is difficult with very small or very large probabilities, but you could cultivate the habit by thinking of various events that have similar probabilities).

        Estimate expected utilities of your choices from your emotional response to imagined outcomes (once you have an intuitive grasp of the probabilities, your emotional response should take them into account). When in doubt, err on the safe side.

    • Margin

      If the numbers are largely made up, it really is a fallacy.

      But if they reflect best guesses on reality, it is useful for reasoning under uncertainty.

      Discounting and risk aversion aren’t obligations or norms, just facts about most people’s actual choices.

      • VV

        If the numbers are largely made up, it really is a fallacy.

        So they seem.

        Discounting and risk aversion aren’t obligations or norms, just facts about most people’s actual choices.

        If you try to model your preferences explicitly and you omit these while they exist in your preference system then you are making a mistake.

      • Margin

        You may have akrasia but the preference to act as if you didn’t have akrasia.

        A strong time preference may simply be based on impulsiveness, while you would prefer to be less impulsive.

        Risk aversion may simply be based on how thinking about risk makes you feel, while the full scope of potential gains are ignored.

        I find it absurd that, if someone decides on reflection that he would rather correct for these, someone else declares he shouldn’t.

      • VV

         

        You may have akrasia but the preference to act as if you didn’t have akrasia.

        A strong time preference may simply be based on impulsiveness, while you would prefer to be less impulsive.

        Yes. So you can try to compensate for them into account by focusing on egosyntonic emotional responses.

        Risk aversion may simply be based on how thinking about risk makes you
        feel, while the full scope of potential gains are ignored.

        Risk aversion is, by definition, how thinking about risk makes you
        feel. What is your point?

        I find it absurd that, if someone decides on reflection that he would
        rather correct for these, someone else declares he shouldn’t.

        If you are trying to build an explicit model of your preferences and you miss important features then you are doing it wrong. Using that model for decision making will make you less happy on average than you would have been if you used a better model.

      • Margin

        VV:

        “Risk aversion is, by definition, how thinking about risk makes you feel. What is your point?”

        The point is exactly what I wrote in the very sentece you quoted:

        Focussing emotionally on the risk, you may ignore the full scope of the potential benefit if the risk doesn’t happen.

        “If you are trying to build an explicit model of your preferences and you miss important features then you are doing it wrong.”

        Exactly.

        This is why you have to correct for risk aversion and time preference if, on reflection, you find you would rather go with expected value.

        I see no need to discuss this further.

      • http://juridicalcoherence.blogspot.com/ srdiamond

        If the numbers are largely made up, it really is a fallacy.

        But if they reflect best guesses on reality, it is useful for reasoning under uncertainty.

        The account tacitly on offer (by said “rationalists”) is that our “best guesses on reality” (on some things) are “largely made up.”

        Their real fallacy lies in their failure to recognize that when information is sufficiently unreliable, it is worse than nothing: it becomes an impediment to global intuition and sense of proportion.

      • VV

         Indeed, that’s the fallacy of fake precision: http://www.fallacyfiles.org/fakeprec.html

  • Michael Mouse

    On general background knowledge, I think your estimate for the extra risk in walking with active use of the phone way too low.

    It’s very widely known that drunk driving massively increases the chances of an accident: I don’t have figures to hand but from memory it’s at least two orders of magnitude, possibly three. (100-1,000x)

    It’s also fairly well established driving while using a phone impairs drivers to a similar degree as being drunk. Estimates vary, and depend on the activity (hands-free calls impair driving significantly, texting quite spectacularly more so).

    It seems very likely that the risks from walking when impaired increase by similar factor to those from driving. So I’d guess you’re underestimating the enhanced risk from phone use by a factor of 30-300, which rather changes your calculation.

    Also, the increased risk is from a higher baseline: deaths per journey are similar for walking and driving, but deaths per hour are about twice as high for walking, and deaths per mile (or km) travelled are about 20 times higher for walking.

    So if you would choose not to drink and drive because of the risk, you should almost certainly not use your phone while walking. At least, not if you want to take a consistent approach to what you regard as an acceptable risk.

    (If you choose not to drink and drive because of the chances of being caught and prosecuted, your calculus may be different: there are currently no legal penalties for using your phone while walking.)

    There are other risks besides personal injury or death that may be worth including in the calculation. Some commenters have already mentioned some of these. Reduced situational awareness probably puts you at significantly enhanced risk of mugging or other interpersonal crime, for instance. Particularly if you are not paying full attention to your surroundings and also happen to be holding a very expensive gadget in full public view and easy grabbing position.

  • Michael Mouse

    Ok, I was wrong about the enhanced risk of death from driving drunk: I can’t find proper stats, but Steven Levitt says (http://www.freakonomics.com/2009/12/14/what-bothers-people-about-superfreakonomics/) it’s 13x, and the risk of walking drunk is 8x that of walking sober.

    Which would make your estimate of 3x within an order of magnitude, though still a substantial underestimate.

    The point about relative risk from drunk driving and phone walking stands, though, I think.

  • Sam Hammon

    “Exercise for 20 minutes, and you gain two units of microlife.”

    So I can convert 20 minutes of my time today into 60 minutes of extra time alive? I think I’ve discovered the secret to immortality! 

    • http://www.gwern.net/ gwern

       > So I can convert 20 minutes of my time today into 60 minutes of extra time alive?

      Just don’t ask about the marginal return on the additional units of exercise…

  • Alex Flint

    If you contribute to x-risk reduction during your life then the magnitude of negative side of this calculation increases substantially while the positive side does not.

  • decius

    Limit your device use to cases where you can retain situational awareness. That means stopping whatever you are doing on the phone whenever you see something that you should have noticed earlier (e.g. another pedestrian) but didn’t, and whenever you anticipate that you might need to react quickly to something (e.g. when you cross any street).

    For music/audio, I would restrict it to one ear.

    If your goal in walking is to relax, or your goal for audio is to zone out or attend to the audio, don’t do it on the sidewalk or anywhere else other people have a reasonable expectation that you are situationally aware.

  • JScheppers

    Your post is very interesting. I do like your analysis and your beliefs are similar to mine. I would add the following cautions based on my recollections of US Pedestrian Traffic Fatalities data:

    1. Don’t walk Drunk. One third of US pedestrian fatalities occur with intoxicated pedestrians.

    2. Don’t J-walk. One half of US pedestrian deaths occur in roadways where pedestrians are not designated to be. I am aware that in many of these cases it is because no pedestrian facilities are provided.

    3. Be more careful on Arterial roads. I am less sure of this number but close to 40% of US pedestrian fatalities occur on arterial streets. I would add that crossing a street also requires additonal vigulance.

    4. Be more careful after dark. Pedestrians don’t have visibility requirements so if it is dark there is a higher chance of fatalities per mile walked.

    Based on these recollections, when in the daylight and on a sidewalk there is very little added risk with headphones and walking texting/emailing.

    But as an former avid runner, I would not advise running in the street unless you have full control of your sense and take full responsbility for being alive after you enter the domain of the car.