Guns, Guts and Gears

Q&A on GURPS Vehicles

By Sean "Dr. Kromm" Punch

What follows are a few clarifications and answers to questions about GURPS Vehicles, Second Edition. These have been taken from rules discussions on the Internet, and have been edited here for clarity and brevity, and to preserve the context of the discussion. Feel free to send your questions to Dr. Kromm .

Combat and Action

1. Can a vehicle dodge at all if it hasn't made a drift or a bend?
2. Are you automatically considered to be dodging if you do make two drifts or a bend?
3. If you're moving at greater than 80 x MR mph, you'll need to make a control roll to do a 15 degree bend. Do you need to make another one in order to dodge?
4. Can you dodge incoming fire that has a "zero time of flight," like laser fire?
5. A radar- or laser-directed laser would be fearsomely accurate. Can you dodge that? Should such "slaved" weapons get an Accuracy bonus?
6. I know that radar is used to track outgoing shells on battleships, so presumably radar or ladar could be used to track incoming shells as well. Assuming you can achieve lock on, can you shoot down an incoming direct-fire projectile?
-- Douglas Cole

1. No. The Dodge roll does not represent an active attempt to evade an attack; rather, it reflects the effect of evasive movement on the odds that a glancing attack will simply be deflected by PD. If you're not drifting and turning, you're not moving evasively and you don't get a Dodge roll.
2. Not quite. If you make the maneuvers, you have the right to make Dodge rolls. However, dodging isn't something you "do" -- evasive maneuvering is what you actually "do." The Dodge roll simply determines its effectiveness.
3. No. If you have already made all the control rolls for the maneuver(s) that qualify you to dodge, then no further control rolls are required for the dodge. The remark on p. VE147 just underlines the fact that to qualify for Dodge rolls, you will have made some control rolls that turn.
4. Yes. You've taken evasive maneuvers, and the Dodge roll is meant to indicate the odds that they will cause the laser to strike at a less-than-optimal angle, thus glancing off your armor rather than biting into it. We're not seriously suggesting that you're moving your vehicle in response to a mysterious faster-than-light cue that someone has fired a laser!
5. This accuracy is why beam weapons (especially lasers) have huge Acc scores, and why all radar- and laser-directed weapons have +2 to hit (sidebar, p. VE177). This does not mean that evasive action can't still cause an ineffective hit, so a Dodge roll is still allowed.
6. Yes. If a computer running a Gunner program and controlling a radar successfully makes a detection roll vs. a fast, shell-sized object, and the same computer controls an unfired weapon that could realistically be used to shoot down a shell (e.g., a beam weapon or hypersonic railgun), then go ahead and roll to hit. Use common sense, however -- most point-defense weapons will have no effect on solid ammo fired from large guns!

How would you handle the situation where a character has a fast-moving car moving toward him and doesn't realize it until the turn before he will be hit?
-- Kellas Reeves

If it's an accident, the victim may roll vs. DX to avoid the car, but if the driver is trying to run the victim down, that's a Quick Contest of Driving skill vs. DX. In either case, the victim's DX is modified downward by a Speed/Range modifier (see p. B201) based on speed in yards/second minus range in yards (since if the car is far enough off, it's easier to avoid). If this difference is 2 or less, the modifier is 0. Give the victim +1 if he has Combat Reflexes, just as for a defense roll.
EXAMPLE 1: Granny backs out of her driveway and accidentally comes toward Supercop. Range is 5 yards, speed is 15 mph (7.5 yards/second). Speed - range is 7.5 - 5=2.5, giving a -1 on p. B201. Our hero must roll vs. DX-1 to avoid being hit. With his Combat Reflexes, that's a simple DX roll -- easy to make with his DX of 14.
EXAMPLE 2: A mobster pulls out of an alleyway and tries to run Supercop down. He makes his hearing roll, so the GM rules he hears the squealing tires of the black Cadillac when it is 10 yards off. It's moving at 40 mph (20 yards/second). Speed - range is 20 - 10=10, giving a -4 on p. B201. With his Combat Reflexes (+1), this is a Quick Contest of Supercop's DX-3 (11) vs. Guido the Hit Man's Driving skill of 12. Yikes!

Weapon Design

1. If you want to add mass to absorb recoil for a hand-held weapon, how should that be handled?
2. How do you add gas vents and gyroscopes to personal or vehicular armaments?
-- Ray Cochener

1. Add "waste weight" to the gun design before you calculate cost on p. VE109 or apply the hand-held weapons rules on p. VE123ff. Now calculate the cost of the weapon based on its new weight. Finally, apply the hand-held weapons rules, which will automatically reduce Rcl for the heavier weapon.
2. These modifications are presumably intended to stabilize the weapon. Rules for stabilization gear for vehicular weapons can be found on p. VE45. For a hand-held weapon, you can add the cost and weight of this gear to the final cost and weight of the vehicular weapon, then treat the whole thing as a heavier weapon under the hand-held weapons rules.

I've been trying to duplicate some of the weapons from GURPS Ultra-Tech to get a feel for the design system, but I've been having little luck. What gives?
-- Douglas Cole

There's a huge number of weapons in GURPS Ultra-Tech and High-Tech, but prior to GURPS Vehicles, Second Edition, there was no weapon-design system. As a result, the statistics for most of these earlier weapons are merely "best guesses," which means that some of them cannot be faithfully reproduced by manipulating the relatively small number of variables used in Vehicles. We deliberately kept the number of variables down because we wanted to make the system usable. Trying to consistently reproduce all of the weapon stats listed in other supplements would have made the system huge and messy.
In the case of personal weaponry, another factor is at work: The statistics often reflect special cases that Vehicles does not cover, since its emphasis is on vehicular weaponry.

Article publication date: August 14, 1998

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