RPG reality check: Are falls deadly enough in GURPS?

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

Well, are they? 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 your 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

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.

Case in point: 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 and not experimentally, we hope!)

That’s 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. Which 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?

Turning to Basic Set 431 . . . 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 yields the same damage as the 16-yard fall that we want.

Herr Gruber demonstrates the LD100 schwan dive

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

That’s an average of only 14 damage, though. Subtracted from HP 10, our own Bill is left at HP -4 – he’s hurt badly, unconscious, and just plain out of action, but not dead. A very high damage roll 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? At least another 50% damage, I’d think. If the GURPS rules meted out 6d damage for this fall, our Bill would take 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 a bit low, as nearly half of those 6d damage rolls will fail to reach Bill’s death roll threshold. (We’re only looking at a rough LD25 or so here.) Perhaps 7d is better, yielding an average 24.5 damage and placing Bill’s HP neatly between -1xHP and -2xHP – solid “roll HT or die” territory. Low damage rolls will still fall under the death check threshold, but equally high damage rolls will force two death rolls. On balance, it sounds like we’re giving Bill a proper coin-toss chance at future adventures.

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. (Edit 2019-06-02: See the comments for a good argument that +100% damage does the job properly.) I’ll just eyeball things with this: At least where 4- to 5-story falls are concerned, if GURPS boosts its hard-surface fall damage by at least 50%, and as much as 100%, the results would enter the ballpark of this doctor’s claim about LD50 height. As it is, GURPS awards relatively low damage in this fall, perhaps as low as half what it (arguably) should be.

Now, real life is going to involve a lot more complications. The car studies surely involve a variety of surfaces, not just the hard city pavement I picture here; this suggests that falls are even deadlier (as some number of real life cases benefit from softer surfaces). Hit locations surely come into play, too, suggesting we can dial back damage a bit, as some real-world falls will have been made worse by head-first impacts. And so on. 

But that’s not too shabby, as RPG simulation goes! This lowballing of damage is even a welcome thing for PC survival, as they scale cliffs, leap chasms, and wage battles on rooftops. Sure, it means the bad guys also get off a bit easy when the PCs toss them off of heights – but 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).

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 (well, often) 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?

8 Comments

  • 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. : /

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