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imp_fireball
2009-10-26, 01:26 AM
If a vehicle is speeding in a hollywood movie, and the hero is holding onto it, the antagonist driver will want to drive faster to obviously shake off the hero. In this case, speed alone (and turning, etc.) is what poses a danger for the hero due to air resistance, violent motion, etc.

It doesn't necessarily matter what part of say, a car, the hero is holding onto... what matters might be the fact that the car is more difficult to hold onto than if it were not moving at all.

The stages of grappling involve touch attack, grapple check (followed by opposed grapple check) and room left over for a move action. For simplicity, I rule that the opposed grapple check is the DC for all further grapple checks against the same opponent for each round (for every new round, another opposed check is rolled to set a new DC, assuming the grapple continues in further rounds).

Touching a moving car is easy - The car applies the AC of a moving object (usually 5 if inanimate when ranged or 1 for melee) + its size modifier + the bonus AC due to exceptional speed (in d20 modern there's a small bonus due to speed dependent on relativistic velocities). What would be the grapple DC for a car that's speeding, however? The same for balancing on top of such a car?

Usually the difference between balancing and grappling can be compared with crouching on top of a car spider-man style versus holding onto a car door and dragging the soles of your feet ala grand theft auto.

There's also the matter of the villain shaking off the hero. This assumes that the villain is aware of the hero on top of the car. A simple rule would be the villain making a drive check (or whatever skill applies if not using modern) versus the hero's balance or grapple check.

If the villain is flatfooted to the hero however, what would be the grapple/balance DC? That's the main question.

Teutonic Knight
2009-10-26, 03:28 AM
Grappling rules are hard. Now you want us to apply to grappling a moving vehicle?

Sure, it's possible. I think. I know Mythbusters did something on this but I don't remember their results. Anyway, wait for the people who actually understand grappling to explain it to you.

Altair_the_Vexed
2009-10-26, 03:50 AM
I've ruled on this in a session - this is the first time I've tried to write it out, so it may not be perfect.
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In some respects, I treat the vehicle as a creature under the control of the driver.

The vehicle can't grapple you. It can only attempt to break the grapple.
To make an active grapple check against you (rather than the check to oppose you grapple checks), the driver must perform some sort of stunt (hard turn, hard brake, dash, etc).
If the driver is unaware of you, he does not add his Dexterity modifier to grapple checks against you, see below.
The vehicle's movement rate is not penalised by being grappled.

For the vehicle's grapple check, use the driver's BAB without STR adjustment, and the size adjustment for the size category of vehicle. Add the driver's Dexterity modifier to checks where he is actively trying to throw you off (through stunts), or driving defensively.
Your grapple check against a vehicle is penalised by the check modifier for the vehicle's speed from Table: Vehicle Speeds and Modifiers.
You do not automatically lose grapple checks against vehicle of any size category.
You cannot pin a vehicle more than two size categories larger than yourself.
You may make a balance check at -10 to oppose the grapple check of the vehicle. Balancing on a vehicle is harder than grappling it.

If the vehicle escapes the grapple, you fall off it, and take damage for a collision with the floor, moving the turn number for the speed. This movement may mean you take additional damage from colliding with another object.

IonDragon
2009-10-26, 04:13 AM
I am not familiar with d20 Modern, however I believe Pilot is a skill in most setting wherein you have access to cars. I would allow the driver of the car to substitute a Pilot check for his opposed grapple with modifiers based on speed, and no bonus for BAB (Knowing how to hit things has little bearing on shaking someone off a car).

That way, an experienced drive capable of pulling hairpin turns at high speeds is much more likely to shake off the Hero.

Mulletmanalive
2009-10-26, 02:54 PM
D20 Apocalpse sorted this one by adding a trick for shaking people off your vehicle. i've always used Climb for clinging to things, balance is mostly for not falling over...

let me go look it up for you.

EDIT:
Ok, there's a bit about jumping onto moving vechicles. DC is set by distance, with a penalty based on the higher speed of the two vehicles. Shift one category down if crossing paths and two down if going in opposite directions:

Stationary +1 [don't know why]
Alley Speed +2
Street Speed +4
Highway speed +8
All out +10.

I think the intention is that if you were on foot in the path of the vehicle, there would be no issue and only a penalty based on their speed, while grabbing the side of the thing counts as perpendicular...

Staying on a vehicle: There is a nice little table here about shaking people off. Absically, it states that staying on a vehilce performing stunts requires a Balance check [or climb check if you're that way inclined] with a DC equal to the stunt's Drive DC.

The exception is the new Shake Off stunt, which has a DC of 15 but causes a DC 20 Balance check.

Apparently, if you roll the car, the people on the outside automatically fall off. I'd personally expect them to get squashed, but that's just me.

Lordy, according to these rules, Bruce Willis has a LOT of balance ranks...