Obviously the ramming rules are shit, and have always been shit, so I thought I'd compile some real world numbers so there's a starting point to try and figure out the game numbers for a more consistent rules set.

First, some rough numbers.

A human falling off a table has an energy about 800 foot pounds. A car crashing into an unforgiving object at 30 mph with a "crumple distance"* of 2 feet exhibits 172,848 foot pounds of energy.

The former would result in "no damage" that would need to be resisted, the latter would probably total an Americar (3500 pounds of weight, which is pretty typical for compact cars today).

An F-16 traveling 300 miles per hour with a 10 foot "crumple distance" would have 13,391,493 foot pounds of energy. Even at a 100 foot deacceleration distance, the energy is still 2,678,298 ft-lbs. Bringing any aircraft to a complete stop is going to be Bad News Bear for everyone involved. Of course, an F-16 has a much higher top speed than that (Mach 1.2 at sea level)...

Now, onto collisions with objects that can move.



Some heavy math is involved, but roughly speaking, when two objects collide, the new velocities are equal to the old velocities, but on the opposite objects (ignoring mass). Two pool balls that collide head on bounce off each other, transferring the momentum from A to B and from B to A. Add in differences in mass, and the larger object changes less.

Car hitting a person:
30 miles per hour, hitting a stationary person (200 pounds) results in the car slowing down by 3.5 mph and the person flying off at almost 56 mph! (assuming an elastic, frictionless, collision).
Using the same calculator I did above, this results in about 6784 foot pounds of energy on the person and 469 on the car.

This sounds about right, hitting someone with a car at 30 mph is pretty fatal for the pedestrian** and not too damaging to the car (dent in the hood, cracked windshield if the pedestrian went over rather than under, neither of which are representative of a "box" of damage in Shadowrun--yes a shattered windshield probably should be, but we have to consider the fact that glass is fragile as all getout and the simulationist nature of the game doesn't respect that).

Real physics equations using game values:
Object₁ will have to be the object with the lower of the two body scores (so an 8 body troll being hit by the 4 body Dodge Scoot, the dodge scoot is object₁ and will use the first equation, the troll the second.
Note: for velocities, these are not relative. If the two objects are moving towards each other, then the lower value needs to be multiplied by -1.

v'₁ = (Body₁ - Body₂) / (Body₁ + Body₂) * (Speed₁ - Speed₂) + Speed₂
v'₂ = (2 * Body₁) / (Body₁ + Body₂) * (Speed₁ - Speed₂) + Speed₂

(And then absolute value the results, because negative damage values are meaningless, although negative velocities are valid)

Hmm...offhand this isn't too shabby and the math, while detailed, isn't that hard (we'll be rounding to whole values in the end, so approximating 3/13 * 10 to "about 2.5"--3 divided by 12 is 0.25, times 10--will be sufficient). Pull out a pocket calculator if you really need to.

Though because speed values are almost already the square-root of their real world mph values...and because the v' values we end up with are what we're going to want as our damage-inflicted values, we need to tweak a few things.

v'₁ = (Body₁ - Body₂) / (Body₁ + Body₂) * (Speed₁ - Speed₂) + (Speed₂)²
v'₂ = (2 * Body₁) / (Body₁ + Body₂) * (Speed₁ - Speed₂)

The lower body object is now taking a pile of damage, especially when hit with a very fast moving object (a speed 10 object will obliterate anything it hits).
The higher body object now only has to deal with the collision of mass, rather than taking a pile of damage based on its own speed (a speed 10 object hitting a pigeon doesn't give two shits).

The +speed on the end was there in the original equation for the larger mass object retaining most of its original velocity (which we actually don't care about for our purposes).

One last change needs to be made.

DV_{Body (lower)} = (Body_lower - Body_higher) / (Body_lower + Body_higher) * (Speed_lower - Speed_higher) + (Speed_higher)²
DV_{Body (higher)} = (2 * Body_lower) / (Body_lower + Body_higher) * (Speed_lower - Speed_higher)

(And round up; rounding normally is fine as well, it makes a difference of 1DV, which doesn't impact the general results much, given the variable nature of the damage resistance rolls)
Now rather than stipulating that Object₂ is the one with the higher body (which plays havok with Speed₂ being 0 when the stationary troll is hit by a careening Dodge Scoot), we instead go "ok, use the larger value here, the lower value there, regardless of which of the two objects are involved." In the case of a tie, both objects use the first equation.
The awesome thing about this is that it works for barriers too. Simply substitute (barrier rating / 2)*** for the body.

A couple of examples, ramming Joe Shadowrunner (Body 4, Armor 9):
Dodge Scoot (Speed 3, Bod 4)
Suzuki Mirage (Speed 6, Bod 5)
Ford Americar (Speed 3, Bod 11) (Yes, it has a top speed of 30 mph)
GMC Banshee (Speed 8, Bod 20)

Dodge Scoot
DV_{Joe, Scoot} = (4 - 4) / (4 + 4) * (0 - 3) + 3²
Both Joe and the scooter resist 9 damage. It's a pretty bad collision, given that the scooter was traveling 30 miles per hour, but no one is killed.

Suzuki Mirage
DV_Joe = (4 - 5) / (4 + 5) * (0 - 6) + 6²
DV_Suzuki = (2*4) / (4 + 5) * (0 - 6)

Joe resists 37 damage, which kills him instantly. The Suzuki resists ~5 DV, which damages the car, but not enough to impair its function. This is pretty reasonable, considering that it was a compact car traveling 120 miles per hour.

Ford Americar
DV_Joe = (4 - 11) / (4 + 11) * (0 - 3) + 3²
DV_Americar = (2*4) / (4 + 11) * (0 - 3)

Joe has to resist 11 DV, which puts him in the hospital, but he'll live. Soccer Mom's minivan however, is pretty much unharmed (2 DV). Given the sheer mass of her vehicle and low speed, this isn't all that surprising. Heck, even a Body 8 troll won't do much more than dent the grill (3 DV) and she can plow through chain link fences all day long (1 DV).

GMC Banshee
DV_Joe = (4 - 20) / (4 + 20) * (0 - 8 ) + 8²
DV_Banshee = (2*4) / (4 + 20) * (0 - 8 )
...Joe's dead. Not even edge can save him now. He'd have to resist 70 DV down to a mere ~14 in order to survive. Still, it's better than the 180 DV he'd have to face by RAW!
The Banshee doesn't even notice (3 DV). A Body 12 dragon might do it some damage though (6 DV, but the dragon would be toast, resisting 66 DV). An 8 Body troll on trollerskates skating towards the Banshee as it hits him will have a noticable effect though (6 DV).

This probably isn't the most accurate thing in the world, but I think I can live with it.

*Aka stopping distance. This value determines how much acceleration the object exhibits.

**
A 10 mph collision ends up giving our pedestrian about 877 foot pounds of energy, which is roughly equivalent to falling off a table, but neither takes into account the impact surface. The numbers I found for falling off the table made note of this and that it was possible for the person to still take a severe injury in that short of a distance.

***Chain link fence has a barrier rating of 4. This would be too large of a value when trying to ram it with a Dodge Scoot, as the scooter probably should be able to break through a chain link fence at top speed.

References:
Impact force (the 800 footpounds for falling off a table)
Cars hitting immovable objects (calculator)
Head-on collision calculator (calculator)
Converting from Newtons to Footpounds (unit converter)

Yeah nobody is ever going to use those formulas at a table. Ever.

So from getting bumped by the car the pedestrian accelerates to almost twice the speed of the car. Not going to happen. Without doing the math i'd say 26mph would be more likely (disregarding energy spent on bending the involved materials).

I have to admit i skipped almost the complete math-part, because i'm not used to calculate in imperial units (metric system ftw ).

Just make an excel sheet from it and you only have to enter 4 numbers.

Feel free to find a formula in the form of AX+C that results in a workable solution where fighter jets don't explode on contact with pigeons.

The first rule is thus:
You NEED to account for both the difference in mass and the difference in speed, otherwise you're going to get wonky results. That's why the formulas look so complicated, but the only part you can't do in your head is the division, but you can approximate that without fucking up the result by more than 1 DV, which is likely going to be inconsequential (either the damage is survivable--most/all resisted, or it isn't--instant death).

Process:
Object 1:
Find the difference in body between the two objects
Divide by the sum of the two bodies
Multiply by the difference in speed
Add faster object's speed squared

Object 2:
Double the lower body value by 2
Divide by the sum of both bodies
Multiply by the difference in speed


The sign values can be ignored in all cases, because the end result needs to be positive.



Considering that the car outweighs the person 17:1...and that the driver isn't hitting the brakes...



The math I put is a pure elastic collision (billiard balls), which a human body is not. It's an inelastic collision, but those are harder to approximate without knowing how inelastic the human body is.

So I'd say that it's a reasonably accurate approximation that can be used to distill down into a workable simulation because we only need an approximation of what goes on, not the exact number of Newtons involved. This section was purely "ok, what kinds of values do we expect in the real world and what is considered survivable?" so that we have a baseline with which to compare our game rules.



Heh, almost all the math I did was done in a mix of units that I converted to imperial for the sake of consistency. The metric system is what makes the numbers work, though.

I don't have any interest in doing so, and have no obligation to do so.

I am pointing out there's a reason that we get crazy vehicle rules that make no sense in reality. It's because trying to model rules on actual physics results in needing to do calculations that 99% of tables aren't going to want to do. GMs will instead just pull a number out of their ass and run with that.

If you can't make a formula that is simple enough for your average gamer to calculate in his head, you may as well just drop that rule entirely, because it is not going to be worth the effort. If we were looking at a computer game, or even a tabletop with heavy computer integration to do the math behind the scenes, that'd be one thing, but that's not what Shadowrun is. And as a result, you have put forth a completely unusable rule to satisfy a level of simulationism that most people don't care about.

And I pointed out that you CAN.

Body 5, Speed 4 vs. Body 3 Speed 1 (away):
2 DV and 10 DV

Body 5, Speed 4 vs. Body 3 Speed 1 (towards):
4 DV and 10 DV

Difference divided by sum: 1 / 9 -> "about a tenth" times relative speed (3) -> going to round up to 1DV + 3-squared (nine) -> 10 DV.
Double the smaller divided by the sum: 6/9 -> "two thirds" times relative (3) -> 2 DV.

Difference divided by sum: 1 / 9 -> "about a tenth" times relative speed (5) -> going to round up to 1DV + 3-squared (nine) -> 10 DV.
Double the smaller divided by the sum: 6/9 -> "two thirds" times relative (5) -> two thirds of six is four, and it's going to round up -> 4 DV.

Took me longer to write out the process than it did to actually do it.

I am frustrated and dismayed at your use of ft-lbs. I can't even look at this until it's in Newton-meters or Joules.

My brain can't think in imperial units.

That part of the post is largely ignorable and fairly stream of consciousness as I worked things out. I was just trying to find a unit of measure to approximate how much energy these kinds of collisions have in the real world in order to gauge if the rules-version resulted in believable results (if falling off a table is equivalent to being hit by a car going 10 mph, then both are largely "injury free", so I should expect 1 to 2 DV from the rules math).

Ok, think of it this way:
Neither the (meta)human body nor the car have any real capacity to store the power of the impact and then release it rapidly (think: rubber ball, spring).
So the two objects collide, each of them starts transforming its kinetic energy into other energy-forms until one of them reaches zero (in this case the pedestrian) at which point it starts to accelerate in the opposite direction.
The car will continue to transfer its remaining kinetic energy into the body until said body has reached the velocity of the car at which point the car can't add any more energy, because the body is already so fast the car can't push it any more.

Sorry for insiting on proving my point (as you already said you used a pure elastic collision), i just couldn't let such a strange outcome slide.

I'll try to think of a simple solution to this problem, but i suspect it just has too many variables.

Edit: Just gathering a few thoughts....

The 3 basic ramming cases will be:
-chase (2 objects moving in the same direction)
-crash (moving object vs static object)
-kamikaze/chicken (2 objects going at each other in opposite directions)

The damage value has to incorporate both speed as well as the body/structure ratings of both objects.

The damage to one object is always depending on the mass of the other object and the total speed (with a hard cap based on the former, Body x 10 from the table on p.203 looks plausible (so the pidgeon will impact for a max DV of 10).
The scale between vehicles and living beings might be off here. (A big troll (Body 10, 300-400kg) still hasn't he mass of a full blown sport car (also Body 10, ~1t) and that's still a lot less than 1/2th of tank, even a flying one (Body 20, ~10t(?)).)

So for simplicitys sake i'd probably go for the standard-rules, adjusted for a few obvious errors* and some common sense.

*As stated above ramming another vehicle gets you damage based on the other vehicle and not on your own.
So, replace:
-p. 203 "Ramming: "The ramming vehicle must resist only half that
amount (round up)" with "The ramming vehicle must resist damage based on the body (modfied by speed according to the table) of the target reduced by the net hits"
-p. 204 "Ram": "The vehicle that did the Ramming takes damage equal to half its Body" with "The vehicle that did the Ramming takes damage equal to the targets Body reduced by net hits"

Damage for very low speeds is only applicable if the target is backed to a solid object (and capped by it's structure-rating + armor).

This is where I disagree. A fighter jet flying at mach 1 hitting a pigeon shouldn't have to resist 10 DV. The pigeon literally explodes and imparts no force on the fighter jet: it's imply too small.* A bird is unlikely to do more than 2 DV worth of damage (before resisting) regardless of what speed it hits or is hit by and aircraft.

Exceptions such as called shots to the air intake manifold, of course.

*Gee golly willackers, aren't bullets small? Yes, yes they are. They are however, very dense, unlike a bird, metahuman, or most vehicles. The force imparted by the bullet is spread over a much smaller area (less if its not tumbling) and the physics on that scale operate differently (very high point-force causing a structural failure of the material, rather than crumpling the vehicle as a whole).

http://en.wikipedia.org/wiki/Bird_strike

Moving on.

I'd say it just means an aircraft capable of supersonic speeds (i.e. speed 7+) should at least have an armor value of 10 and therefore ignores such a damage amount (not RAW but makes some sense).

(A pidgeon should really have only a fraction of Body 1, but thats not covered in the rules.)

According to SR1, a bat had a Body of 1.

Just a reminder: most things that kill you outright in real life won't necessarily do so in Shadowrun. SR5 raised the DV of weapons so it might be different, but in SR4, it was unlikely to kill someone with one bullet or with one sword strike, and poisons were also less effective than they're supposed to be. So if SR5 still has that "no one-shot weapon" concept, having cars be as deadly as in real life would make cars better than other death-dealing options.

there are a ton of examples in the real world of one bullet or sword swing not killing people.

And just as many that do...

You are greatly overestimating the average gamer's tolerance for math.

In general, for game design, you want to avoid more than two math operations on any given task. The method you suggest requires five to six operations.

What may be simple to you is not the same for everyone else. Or at least, even if others are capable of doing the math, they may not have the patience for it.



-k

Le sigh. Where are the old days where D&D listed damage as 3-12 and forced the player to figure out what that actually meant in terms of dice (3d4? 1dd10+2?).

From my experience, the biggest issue is on the fly math. If you need a calculator or Excel before the game starts to crunch some numbers that's not a huge deal - they could always ask for help or take their time. At the table? Not so much.

The ramming rules are hilariously broken, but I'm at a loss of how to fix them right now aside from a Band-Aid or three. A full fix would probably take a larger chunk of text than what is in the book so it can't easily get errata. It's treated as an edge case in the book, so it's also unlikely there's any urgency by Catalyst to fix them.

Threads like this are great for hashing out some worked examples though. I hope to have something more concrete to add for modified vehicle rules in general at some point in the near future.

Alternate rule -- slightly harder than the base rules, but easier than my Physics 101 homework:

Step 1 -- Calculate Speed of Impact:
-chase (2 objects moving in the same direction) = Faster speed minus slower speed
-crash (moving object vs static object) = Speed of vehicle
-kamikaze/chicken (2 objects going at each other in opposite directions) = Faster Speed + Slower Speed

Step 2 -- Consult the Table on SR5 p. 203
All Body DVs are based on the damage of the impacting item, not the resisting vehicle.

Step 3 -- Soak Damage

Example: Body 2 person standing still vs Body 20 tank advancing at 10m per turn
Person soaks 10 (1/2 * 20) and Tank soaks 1 (1/2 * 2)
Odds are good that the person will die, and if not, the next tank in line will finish the job.

Example: F-16 Birdstrike -- Use GMC Banshee at 501+ m/turn
Bird soaks 200 (10 * 20) and Banshee soaks 10 (10 * 1)
The bird is turned into a fine red mist, and with 38 dice odds are good that the Banshee is unharmed. At a 4:1 trade-in, takes 1 box of damage.

That's actually fairly reasonable.

I'm honestly very leery of using the Ramming Damage Table. I would like to see Speed used directly, instead of this weird doubling speed per Speed point and then look at a mostly linear table.

How would you handle Barriers? Those appear to be problematic even with this fix.

Example: Body 20 light tank advancing at 10m per Combat Turn rams a brick wall (Structure 10).
Wall soaks 10D with 26d (Structure + Armor). Tank soaks 5D. Tank might not break the wall but isn't hurt, either.

Example: Body 11 Americar at 'top speed' crashes into plastiboard (Structure 4, Armor . Wall soaks 11D damage with 12d. Good chance that plastiboard is no match for the mighty Americar. Car takes 2D. Ok no problem here.

Example: Body 20 LAV hits brick wall at max speed.
Wall soaks 200D damage with 26d (boom! Probably opening a 16+ meter hole). Banshee soaks ... 5D? If It rams reinforced concrete it only resists against 7D? Even if you use full Body that's only 14D. The "balance" (such as it is) with the current rules prevents this because you immediately detonate yourself. And now that 200D LAV can ram tanks all day long because he's only taking 10D or at most 20D in return.


Your fix immensely helps with the birdstrike problem, but if anything exacerbates some problems with barriers (at let's be clear, I think this is a problem with the barrier rules, not the vehicle rules). This is why the problem is seemingly intractable, all these systems that were designed independent of each other and are not based on any physical principles don't work great together :/

Tzeentch -- I think the problem is you only assigned the speed to one side for the barriers. If we use Structure instead of Body, it still works out.

Banshee at full speed into Brick wall

Step 1 Calculate Speed -- Crash (1280 - 0 = 1280)
Step 2 Consult the Table -- 1280 is in the 501+ so Body x 10
Step 3 Soak Damage

Banshee soaks 100 (brick wall 10 x 10)
Brick Wall soaks 200 (Banshee 20 x 10)

Both are going to be obliterated.

-----------

Tank vs Wall
10m/ turn = Body/2

Wall soaks 10
Tank soaks 5

-----------

Americar vs Plastiboard
20 or 40 m/turn falls in the same range = Body

Wall soaks 11
Americar soaks 4

Would it be possible to do a chart for it? Have the math for Object A and the math for Object B calculated via chart, then compare the result of A and B on a different chart? That could help things along, possibly.

Since we're proposing alternatives, I'll throw out one that's slightly less math intensive and does not require the using the table in the book.

DV = (Difference in Body) + (Difference in Speed)x2 + net hits on driving test (or other applicable test)

If the difference in body scores are in your favor, they step the damage down and if they're not they add to the damage. It's like reach. Pretty easy to calculate, pretty easy to remember. Probably still some weird edge cases, but works well for most normal ranges. That is it works well for damage ranges we like at our table. Threatening and maybe kill you but not instant kill-never survive-even with edge-one shots a great dragon damage ranges. Difference in speed calculated based on whether the object is stationary, being chased, or ramming each other (i.e. head on collisions add speed scores together, yeah I know because of the speed numbers it's not exactly right, but whatever)

To use the examples from the first post:
Body 4 runner vs. (assuming runner standing still)

Scooter:
Scooter resists: 6 DV
Runner resists: 6 DV

Low, but it's a fairly low speed collision afterall. And someone being rammed to death by a scooter doesn't really scream common play scenario to me.

Mirage:
Mirage resists: 11 DV (should have bought american)
Runner resists: 13 DV

Americar:
Americar resists: 0 DV (the body difference stages down all the low speed damage)
Runner resists: 13 DV

Banshee:
Banshee resists: 0 DV (saves time rolling for damage it would have resisted anyway, though traveling at speed 8 anywhere it could hit a human target you probably need to worry about the thing you hit after the runner)
Runner resists: 32 DV

You can replace the Body rating with structure for barriers.