RPG reality check: Are falls deadly enough in GURPS?

Are falls properly deadly in GURPS? Over a wide range of fall distances, impact surfaces, character sizes, etc.? I dunno. But here’s one interesting piece of data – an expert’s claim, anyway – that we can use to match one real-life situation against the results generated by an RPG simulation, and see how the two compare.

So go get some favorite GURPS characters, nonchalantly lead them to the rooftop of a four-story building, and push them off! Let’s see how many survive.

Falls and the LD50

Nothing messes up a mortality study like a Sean Bean in the cohort

The AV Club article “Allow this trauma surgeon to ruin a few of your favorite action scenes” introduces a video in which trauma physician Dr. Spiros Frangos reality-checks the hurts he sees in movies.

When Tom Cruise drove his car off of a parking garage floor in Mission Impossible: Ghost Protocol, Dr. Frangos says the character should not have walked away easily (if ever). Maybe. This is actually a hard one to call, as it’s an unusual fall, what with the car and seat belt and air bag and all that.

But for the far more common case of a fall victim who’s not handily ensconsed in a steel cocoon, the good doctor points us to “LD50”, or the “height at which 50% of patients are likely to die” – and names 48 feet (16 yards), or about 4 stories, as the LD50 height. (And how was this information obtained? Anecdotally, we hope!)

That claim is something we can place up against game rules! We’ll have to make assumptions, of course; namely, that the data behind the LD50 claim represents people of all ages and sizes, and thus “average” people overall. (This isn’t necessarily a correct assumption. It’s conceivable, as an example, that extreme sports fans and other daredevil types, who tend to be young and fit, are over-represented in high falls. Or that very young and old persons, with more limited coordination and awareness of surroundings, are over-represented in high falls. I don’t know.)

This means we’ll be dropping an average HP 10, HT 10 GURPS character, with no special traits assumed. We’ll also have to ignore real-life complications for which we don’t have information – e.g., to what extent the fatality statistics are lessened by landings on softer surfaces, or are worsened by head-first impacts (something not explicitly made an outcome in GURPS rules). And on the game rules side, we’ll ignore the complications of mortal wound results (which make proximity of medical care a factor) and optional rules like bleeding.

Those considerable caveats notwithstanding, where damage and death are concerned, this LD50 stat sounds like one of the cleanest claims we could test in-game.

So what’s the damage?

Herr Gruber demonstrates the LD100 schwan dive

We turn to Basic Set p. 431, and… Hey, this is easier than I expected! That page’s example of a fall does all the work for us. It uses an HP 10 victim (“Bill”) and a fall of 17 yards, which is treated as identical to the 16-yard fall that we want. So let’s just read from the book.

Bill meets the ground at 19 yards/second, which would be (10 x 19)/100 = 1.9d damage – but hard pavement doubles that to 3.8d damage, which rounds up to 4d crushing

Sounds painful… but it’s an average of only 14 damage. Subtracted from HP 10, our own Bill is left at HP -4 – he’s hurt badly, unconscious, and just plain out of action, yet not dead. A very high roll on 4d could kill him, but we’re surely not getting our LD50 with this fall. (A fall onto soft ground, meanwhile, isn’t likely to even render Bill unconscious!)

Dialing up the hurt

So, what adjustment would make a GURPS 16-yard fall better match reality? Let’s try boosting damage by a healthy 50%. The above 4d damage becomes 6d, so our Bill takes an average 21 damage – just enough to push him over the negative HP line, and thus forced to make a death roll. Which, at HT 10, means a 50/50 chance of dying – exactly what LD50 calls for.

But that’s still too low! About half of those 6d damage rolls will exceed Bill’s death roll threshold, but that doesn’t make him more dead. (No roll on 6d will be high enough to force two death rolls.) Meanwhile, nearly half of the rolls will fall short of forcing even a single death roll. Really, we’re looking at a rough LD25 or so here – about 50% of the damage rolls will force a 50% chance of dying.

Double impact!

I’ll leave it to anyone interested to fiddle with the exact distribution of results and come up with a precise calculation of the damage dice that would yield a perfect 50/50 chance of survival in this fall. Until then, there is a good answer, and it’s an easy one, too. In comments below discussing an earlier version of this article, commenter Rasputin suggests a clean doubling of damage.

Doubling GURPS‘ 4d to 8d, we get damage that ranges from 8 to 48 points, with 28 as the average. Low rolls still won’t force a death check, but a high roll can force two or even three rolls. Most importantly, an average roll leaves Bill firmly between -1xHP and -2xHP – solid “roll HT or die” territory. Maybe I’ll work out the exact percentages later, but for now I think we’re close to LD50, with Bill’s appearance in future adventures pretty much a coin toss.

So, to give things a quick eyeball: At least where 4- to 5-story falls are concerned, we need to substantially increase fall damage if we want to simulate the doctor’s claim about mortality. Boosting fall damage by 50% gets us closer to the mark; cranking it up by a clean 100% appears to nicely mimic the doctor’s claim.

Or keep it low

Let’s note again that real life involves a lot of complications. Real case studies surely involve head-first falls that increase mortality, as well as falls onto softer surfaces that decrease mortality. I have neither the data nor the inclination to delve deeply into these. (And it’s worth noting again: we’re reality-checking a game fall of one specific height, not falls in general!)

Whatever the most realistic damage roll for a given fall might be, GURPS‘ by-the-book damage seems pretty low, perhaps even half what it (arguably) should be. But that’s not too shabby, as RPG simulation goes! I’ve seen games with far less realistic damage rules. And GURPS‘ lowballing of damage is a welcome thing for PC survival, as the heroes scale cliffs, leap chasms, wage battles on rooftops, and – oops, now it’s an abrupt return to Mother Earth’s embrace, the hard way.

Sure, lowballed damage means the bad guys are also handed a break when the PCs toss them off of heights. But in practice, that doesn’t help them much. A dropped mook who’s “merely” knocked out is still out of the fight (and is soon out of it for good, if the PCs are vengeful “finish the job” types). For them, the result is typically the same.

So. Keep GURPS‘ falling damage as it is if you want results that are survival-friendly (though still plenty deadly when the heights are high enough or the rolls bad enough). Double the game’s falling damage if you want heady realism (at least for some falls).

Either way, remind your players to take care. However harsh a mistress you decide gravity should be, she’s rarely a PC’s friend.

Last line

Well. That was mildly amusing, if not terribly useful. Heading back to the good doctor, I like how he ends the video:

As a trauma surgeon, when I go to the movies, I’m always thinking about the realism of particular injuries, to the fact that sometimes it ruins the movie for me.

I think we can appreciate that! Because as a gamer, when I go to the movies, I’m always thinking about how the screen action maps to game simulation. To the extent that even a discussion about movie action gets me rolling dice in my head.

You too, maybe?


  • Rasputin

    Would changing the divisor from 100 to 50 in the formula do the trick? For the Basic Set example, 10*19/50 comes out to 3.8, or 4d, doubled to 7.6/8d on hard ground. Average damage on 8d is 28 HP, which triggers a death check. A not-especially-aberrant roll is 30 (38.02%), which triggers two death checks.

    Let’s look at it this way: 96.11% of all rolls get at least one death check, 38.02% get at least two, and 0.74% get three. Of the one death check crowd (58.09%), half (29.05%) will die. Of the two death check group, three-fourths (27.96%) will fail, and of the three death check group, seven-eighths (0.65%) will go. That’s 57.65%, and some of these guys are merely mortally wounded and saveable with a Surgery roll.

    • tbone

      Assuming your math works out – and at first glance, it appears to – you may have the best solution. If doubling GURPS‘ fall damage yields a 57% death rate for normal PCs, that’s darned close to the 50% rate we’re looking for. It’s a little more harsh than we’d like, but as you point out, some of those “deaths” will actually be mortal wounds that might be salvaged, dialing back the mortality toward 50%. And as an added bonus, “double the damage” is easy, too!

      So there you go. Unless someone’s got a good counterargument, I’d suggest doubling GURPS‘ falling damage to anyone looking for the most realistic (and not heroically survivable!) damage possible.

  • Raving Nutjob

    My takeaway is that this might be really interesting if one was designing a falling damage based dungeon. Think a shonen/wuxia based place with a series of guards, skilled in arts like grappling and throwing, prepared to fight in locations with conveniently accessible drops. Whether a pagoda, or the sides of a mountain, or whatever. Could be a lot of fun.

    • tbone

      Nothing wrong with lots of falls in a dungeon! A structure with lots of collapsed portions, or any natural cave, could be one great series of climbs, chasms, pits, and plunges – all it takes is more vertical thinking by the GM. PCs with Catfall – a rather expensive advantage, IMO – will get to have some fun. (And re grappling and throwing, as you mention: yes, skills like Push and Immovable Stance are kind of dull on the generic flat battle map, but they become awesome on ledges and other narrow perches. Any knockback, in fact, becomes more fun. Time for big, heavy, crushing weapons to shine!)

  • Rasputin

    Well, if the average PC has HP 10 and HT 10, life is cheap in those games anyways.

    Most PCs have plenty of ways to survive the fall, like more HT, Luck, and Acrobatics. An average Dungeon Fantasy or Action character has HP 12 and HT 12. That means the fall will do 9d damage (ignoring the static fall table used in Dungeon Fantasy and Action). One death check is 94.04%, two is 22.04%, three is 0.05%. Pretty similar; attribute the difference to the fraction being rounded down and not up. With the higher HT, I get 28.62% death rate. Again, some of those deaths are survivable after a Surgery roll. A successful Acrobatics roll drops the damage back down to 8d, and the one/two/three death check percentages are 82.11/6.07/0.00% (getting 48 HP damage is one in 1,679,616), giving us a 22.45% death rate. And then there’s Luck …

    • tbone

      Yeah, PCs are mighty tough. A GM could double GURPS’ falling and impact damage, and PCs would still fare pretty well.

      Now, if you’re explicitly going for a Peter Jackson feel in your game, you want to multiply all fall and collision damage by, oh, 0.1 or so. Or just flip a switch that says “Falling off cliffs or slamming into stone walls will inconvenience PCs for 1d6 seconds.” : )

  • PvK

    If like me, you use the optional rules on bleeding (B420) (I actually use a version the multi-wound bleeding rules from GURPS Compendium, but that’s another matter), then I wouldn’t necessarily want the damage to kill someone outright.

    That is, I think of death by death check on the turn the injury was done, as being killed immediately, which is not what the medical people mean by a fatal injury. Real people often die minutes or hours (or days) after a serious injury.

    Average Bill taking average 50-foot falling damage of 14, makes bleeding checks at -2 HT (would be -3 if he had taken 15 points of damage). It’s pretty likely even at -2 that unless someone shows up and manages to stop (internal?) bleeding in the next 6-10 minutes, that Bill will be making a death check.

    I’d say that if you use even the Basic Set’s optional bleeding rule you already get close to a 50% chance of the 50-foot fall to concrete being lethal without prompt medical attention.

    If you use the juicy optional “I’m Not Dead Yet!” rules from GURPS Compendium II pp.154-156, the odds get much more complicated, and probably deadlier, as a fall could cause up to 4 injuries, each of which could bleed, so someone could lose up to 4 points per minute, and/or may be more likely to suffer a lot more bleeding damage if no doctor is on hand…

    And yes, I always think about how movie events would map to a game, and am frequently annoyed, especially when some series switches writers and apparently game systems (GRRM played GURPS, but the season 8 writers are doing some ridiculous story-game where the goal is for them to contrive scenes for dramatic effect, with no other reasoning behind what happens).

    • tbone

      You do a good job of highlighting why reality-checking something like this can never be more than guesswork.

      On the reality side, there are the questions of what data is and isn’t going into these death statistics, how many of the deaths are instant vs much later (with what sort of medical care involved), what are the conditions of the incidents (hardness of surfaces, ages of victims, etc.), and much more. (It may be possible to research much of that, but I certainly haven’t do so for this simple exercise.)

      Then, on the game side, there’s the question of what basics to assume (like hard surface or soft), and what combinations of optional rules to assume.

      So: I do think this LD50 stat gives us one of the best opportunities we’ll find to (sort-of) reality check a game situation involving human trauma – but even then, only for a narrow situation, and only by making a bunch of assumptions. Ah well. It still remains a mildly interesting exercise.

      Your point on the bleeding rules is well-taken and helpful.

      To a GM who says, “Look, this is all fine and semi-interesting, but what’s the rule of thumb I can take to the table, to make sure falling damage in my game is generally realistic?”, I would say this:

      If you’re using GURPS’ basic “damage is instantaneous” rules, falling damage appears to be too low for strict realism. Boost falling damage by at least 50%; go a full +100% if you want a solid level of realistic deadliness. Or, leave damage as it is, and let the bleeding rules handle the extra deadliness.

      These look to me like “good enough” rules of thumb to ensure realistic falling damage, if that’s what a GM even wants.

      Maybe realistic, anyway. At least for 50-foot-ish falls. No idea whether it’s all realistic for other heights. : /

  • TGLS

    So I sat down and crunched the numbers (https://1drv.ms/x/s!Ajg1vMLz0uSpr2eUt0H5jfGktTw8?e=ikdiET). Now it turns out that the effects of hit location are less relevant than I thought for falling damage. Neck wounds and skull wounds only increase the lethality of fall damage by about 2-3% points in the standard case, and by about 1% in the doubled damage case. However, the doubled damage case might be making falls more lethal than the LD50 estimate that you’re working with. By my calculations, doubling the damage of a fall increases the lethality to about 58%.

    Given that in the standard case you’re looking at about a 5% (with hit locations) or a 2-3% (without hit locations) chance of death, this is much closer to the general ballpark of how lethal a fall should be, but it does tend to skew things upward a bit. For example, a one yard fall (about the height from the inside of a UHaul to the ground) has about 0.7% chance of death under these rules (with hit locations).

    Should the doubling apply to other collisions too? A five yard slam doesn’t become that much more useful (a punch or a kick does less damage, but a slam needs a running start). On the other hand, it would certainly up the damage from allegedly no damage attacks like shoves and water jets when shoving people into walls.

    • tbone

      “So I sat down and crunched the numbers…”

      Gamers. Bless ’em. : )

      Now, I don’t know how those groin falls work exactly, but the skull falls are an interesting case – amazingly lethal. So many death rolls! Interesting, though, how the infrequency of occurrence makes their difference in the overall results so small.

      In the end, I can see from your work that doubling the game’s fall damage may take lethality slightly past the LD50 mark for the fall in question. With so many other factors ignored, though – the chance of softer ground, the chance of mortal wounds that receive treatment, etc. – I think we can conclude that doubled damage remains in the ballpark of realistic with respect to the LD50 claim in question. Thanks for the rigorous study showing that taking hit locations into account doesn’t totally overturn that idea!

      As for slams: Yeah, I suppose that if we want to achieve brutal realism in falls by doubling damage, it may make sense to do the same for slams too. Though we have no real-life data point to check the results against… : (

  • Maximilian D Wilson

    I like this because the practical effect is just that monsters (and delvers) no longer have to dig implausibly-deep holes for their pit traps. A 10′ deep pit is now[1] 2d+2, which can be pretty nasty if you put spears at the bottom to turn it into impaling damage.

    My only concern here is that it might make it too easy to break a leg or an arm, since damage is inflicted to a random hit location. On 6-8 or 12-16 on 3d6 (57% of the time), you wind up taking damage to your hand or foot, which will pretty much always cripple a normal person’s limb/extremity if the fall is at least 1 yard onto a hard surface (10 HP * 2 for hard surface * 5 for velocity from 1 yard * 2 for doubling/100 = 2d).

    That’s too much crippling to be plausible. But it’s not the amount of damage that’s wrong, it’s the distribution. Maybe it makes sense to double the damage, but to roll hit location TWICE and split the injury between those two locations (or just one location if you roll the same location twice).

    • tbone

      I agree with you that damage can be over-concentrated on a limb (with or without any change to falling damage itself). And I like your idea for a more nuanced take on fall damage: split it into two rolls that can affect two locations.

      “Two”, of course, is completely arbitrary; I suppose an ideal system would somehow divvy damage among a number of locations. But two locations is few enough to keep things quick, and – the gist of your idea – it’s particularly easy to use for any GM planning to double damage per the article’s suggestion.

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