from Hacker News

Speeding Slows You Down (By a Lot)

by williamkuszmaul on 1/27/24, 3:21 PM with 126 comments

• by alexwhb on 1/27/24, 5:16 PM

  While the methods in this post may not be a super accurate depiction of reality.. I did find it entertaining. Additionally I agree generally with the point the post is making. It is shocking to me that we accept so whole heartedly the risk associated with driving when, comparatively, it is shockingly unsafe relative to other modes of transportation. In the US somewhere around 41,000 people die per year from traffic accidents. If we compare that to train travel (especially in Europe where safety standards are significantly better) it’s somewhere in the ballpark of 32x safer. Additionally we accept the liability of a car shockingly easily. Yes we all should have insurance, but that insurance only goes so far. If you accidentally kill somebody on a bike you’re likely to serve prison time for manslaughter. There are several other downsides we accept that I won’t get into, but it’s pretty interesting to me that especially US society has accepted these facts so seemingly easily.

• by codeflo on 1/27/24, 4:54 PM

  Why would you add the lost life expectancy to the length of the trip? That doesn’t make any mathematical sense to me.

  Edit (this might be wrong, see Edit 2 below -- I'm leaving this as is because otherwise, some of the responses don't make sense):

  I noticed that the calculation is wrong even within the article's own logic. Supposedly, this calculates "the expected length of the trip (including dead time) at different speeds", and does so by adding the expected loss of lifetime to the total trip length.

  However, you're surely not always going to die exactly at the end of the trip. In fact, you can be expected to die at the half-way point on average, meaning this "total time" in case of death is only half the trip length plus the loss of life expectancy. If you plug this into the equation, the speed that minimizes the travel time dramatically shifts to around 100 mph.

  And more absurdly, near the end of your life, when your mathematical life expectancy might be measured in hours, it's "faster" according to this logic to just kill yourself and get it over with than to undertake any long trips at all. I wouldn't recommend following this line of reasoning.

  Edit 2: The above line of reasoning might be wrong, I think I made an error and the calculation is correct within the article's premises. In that case, I take that part back. I still don't agree that adding loss of life expectancy to travel time is a reasonable way to look at things.

• by bdcravens on 1/27/24, 6:17 PM

  Never mind death, a collision (even a minor one, where you simply exchange insurance information) or a ticket will kill your "productivity" gained.

  I used to be the crazy driver (and occasionally that personality comes out to play), but these days I usually just set my cruise to whatever is practical (in large cities, it's not the speed limit, but a bit higher to match others), and let adaptive cruise do most of the work.

• by jdboyd on 1/27/24, 9:44 PM

  I found this very entertaining. However he also forgot to include anticipated delays from speeding tickets. I'm sure there are other things that should have been factored in as well, such as sometimes increased waits at lights because you arrived earlier at it, so 25 or 65 would make no difference in how long it takes to get to the ither side of the light.

• by tra3 on 1/27/24, 5:51 PM

  I’ve learned “slow is smooth and smooth is fast” from shooting sports, but I find it applies equally well to most (all?) areas of life.

  When I started driving, I used to speed to the next stop light, change lanes frequently. I stopped doing this when I got older, partially because I see people that zip around at the same stop lights anyway.

• by m1n1 on 1/27/24, 6:28 PM

  Driving aggressively occasionally causes others to slam on the brakes to avoid accidents, which creates standing waves also known as traffic jams. So speeding at least slows everyone else down.

• by barrkel on 1/27/24, 5:04 PM

  Well I guess if you die, then your trip took infinite time (you never arrive), so it does tend to push up your probability weighted average. But it's a push.

• by tzs on 1/27/24, 5:07 PM

  Note that there are some types of accidents whose probability goes down the faster you go. An example would be getting hit head on by someone who veered out of the opposite lane into yours.

  The probability of being in that kind of accident goes up as the number of cars that you pass in the opposite direction goes up.

  Without loss of generality we can assume that there are no entrances or exits on the other lane between your starting point and ending point, because if there are we can simply treat you trip as a sum of separate trips between each pair of consecutive entrances/exits.

  The number of cars you pass going the opposite way is the sum of the number that were on the road between your start and end point when you started and the number than enter the road while you are traveling.

  The number already on the road does not depend on your speed. The number that enter while you are traveling does, going down the faster you travel.

  Hence the faster you go the lower your chances of getting hit by a lane crosser.

• by jp57 on 1/27/24, 5:11 PM

  When people say “the probability doubles” they really mean that the odds double, right?

  If my probability of dying is .6, it can’t double to 1.2. However if my odds of dying are 3:2, they can double to 6:2 or 3:1 or P=0.75. The odds can continue doubling indefinitely and P will asymptotically approach 1.

• by whoopsie on 1/27/24, 4:57 PM

  These numbers poke only a narrow solution. The optimal fastest way is to have the destination speed to you.

• by LorenPechtel on 1/27/24, 9:04 PM

  And to throw out another factor that messes up this analysis:

  Most accidents involve the interaction of two cars. The faster vehicles get to their destination the fewer vehicles are on the road at any one time and thus the fewer interactions there will be.

  I have no numbers on how big an effect this would be.

• by standardUser on 1/27/24, 5:44 PM

  > Maybe highway miles are much more dangerous than non-highway miles, and we shouldn’t be on the highway at all.

  I imagine it's pretty hard to get seriously injured or die when not on the freeway. I've long thought that should be the primary application of self-driving technology. It's ultra-simplified and relatively standardized compared to other types of roads, and it's where the most life and limb can be saved. Not to mention the potential to alleviate traffic, which would save people vastly more time than just driving too fast.

  Also, will everyone please use you blinker for fuck's sake? If moving your wrist slightly is just too much of a burden for you, then stop driving, you're not cut out to pilot your own anything.

• by ilovecurl on 1/27/24, 6:08 PM

  "An odd feature of the model is that, the older you get, the quicker your trips become, at least in expectation, and the more you should speed."

  I am reminded of the track from The Dead Kennedys, Buzzbomb from Pasadena.

• by iJohnDoe on 1/28/24, 3:37 AM

  FWIW - just estimates. I had a 30 mile commute. If I drove 65-75 I could make in about 25 minutes.

  One night I was on-call and drove really fast in the middle of the night and it took about 18-20 minutes.

  I realized it was never worth it to shave off a handful minutes and drive way too fast to any destination.

  Basic math. When you get to a certain speed, you’re shaving off seconds/minutes. 65mph is certainly better than 35mph. 90mph isn’t really better than 65-75.

• by bagels on 1/27/24, 6:25 PM

  If you die, this doesn't increase trip length. I'm not sure I'd care how long it took if I were dead even if it did.

  When the trip is completed successfully, you've arrived sooner and the habit of speeding will only then affect risk on future trips, there is no post facto cost (ignoring automated speed traps).

• by tim333 on 1/28/24, 12:10 PM

  Including changes to life expectancy can be an argument for cycling if you are middle aged. What it takes in terms of accidents and pedal time it gives back in less heart attacks.

• by tdrz on 1/27/24, 6:09 PM

  I think it remotely applies to working, as a founder, at a startup. You might go real fast for a while, but then you (might) burn out and quit altogether.

• by pierat on 1/27/24, 6:28 PM

  Not driving at all is infite speed to your destination?

• by 1970-01-01 on 1/27/24, 5:57 PM

  I love a good bullshit analysis. Yes speed kills the average driver (the one with one ovary and one testicle) so you shouldn't do it. In fact, you'll get there sooner by going under the speed limit. Your mileage does not vary.

• by JackSlateur on 1/28/24, 12:15 AM

  It is funny how much people correlate speed with death rate

  Better correlate death rate with Time spent on the road

• by giantg2 on 1/27/24, 5:17 PM

  This is idiotic. The penalty wouldn't apply to the trip if you didn't incur it (die) during the trip.

  Also, as they noted, there are a bunch of other factors. Some of those factors are equally or more important as the ones they are looking at, such as alcohol impairment (both about 30% of traffic fatalities).

  The biggest fatality risk factor is not being buckled in. About 45% of all occupant fatalities are people who were not buckled. This will greatly skew the stats if not properly accounted for.

  Edit: why disagree?

• by photochemsyn on 1/27/24, 5:14 PM

  The safest driving speed on busy roads is the speed everyone else is going. If everyone would drive this way, overtaking accidents (often very serious injury-wise) would be eliminated.

  This means slow drivers are just as dangerous as fast drivers, and also points to why self-driving cars would greatly reduce highway accidents. Assuming they'd all be monitoring each other's speeds, they could coordinate like swarms of drones, and thus could drive safely at faster speeds.

  To go even faster, the cars could link up into a single line, under coordinated control, and zip along like a high-speed train (which is why trains are the most efficient transport system, at a nice optimum balancing speed and energy consumption). However, this 'train of cars' has some advantages, as you could then just detach from the train and drive on independently to your local destination, avoiding the last mile problem.