D20 Chase Rules
These d20 Chase Rules are adapted from the rules first presented in the Spycraft main book.
Contents
The Chase[edit]
Chase scenes, when done well, can become a long talked about moment in any d20 game. Traditionally the classic d20 chase has consists of little more than two dice rolls and the declaraing the winner. These rules and some spice and variety to the action. The core rules assume the use of land-based vehicles (Cars, Horses, Stagecoaches, etc.) Rules for alternate chases follow the main rules.
Transport Stats[edit]
Transports use a short list of stats detaled here.
Defense
The base Defense stat. Basically the vehicle itself before taking into account the pilot's skill.
Handling
How well the vehicle handles. This will either be a boon or hinderence as the stat is added to maneuver checks.
Hardness
Material strength of the vehicle. Functionally acts as it's armor subtracting damage from certain types of attacks.
Size
How big the vehicle is DUH!
Hit Points
Once the vehicle hits 0 it's time to find a good mechanic.
Getting Started[edit]
The rules are intentionally free form to encourage DMs and players to describe the elaborate events of their chase. Feel free to drop in a chase wherever it feels right.
The chase begins when one vehicle (dubbed the "Predator") tried to catch another (the "Prey").
Terrain[edit]
Different types of terrain pose different threats and opportunities.
Open Terrain
Wide open spaces: Empty roads, flat deserts.
Chases start at 3/4 of the top speed of the fastest transport involved. The transport with the higher max speed gains a +2 speed bonus to manuver checks.
DMs randomly roll a d10 every round, a 1 indicates a dc12 obsticle has cropped up.
Closed Terrain
Closer space: City streets, winding dirt roads.
Closed terrain chases start at 1/2 of the top speed of the fastest transport involved.
DMs randomly roll a d6 every round, a 1 indicates a dc18 obsticle has cropped up.
Tight Terrain
Small space: Crowded market, Steep hill, Battlefield.
Chases start at 1/4 of the top speed of the fastest transport involved. The transport with the higher handling gains a +1 speed bonus to manuver checks.
DMs randomly roll a d4 every round, a 1 indicates a dc24 obsticle has cropped up.
Inital Lead[edit]
The distance between the Preditor and Prey is known as the "Lead."
During a chase you use units of Lead to determine the space between the transport. One unit of lead equals 10ft (although it could be adjusted to any unit of mesurement you'd like).
The Lead can never go below 0 or above 30. If the Lead goes above 30 then the Lead stays at 30.
However the chase begins in the story, deside wether it was Predator or Prey initiated.
If the Predator begins the chase, the prey's inital lead is 2d6+3 x 10ft. If the chase starts with the Prey running away then their inital lead is 2d6+8 x 10ft. In the case of a tie, (i.e. no clear initiator) roll initiatlve.
Speed[edit]
Chase speed is measured in miles per hour (MPH), and is determined by terrain at the start of a chase. Chase speed changes throughout the chase according to the maneuvers chosen by the both pilots each round.
Whenever the chase speed exceeds the maximum speed of one or more involved transport at the end of a chase round, the transports in question each take 4 points of damage (reduced to 2 if the driver has the Daredevil ability). This damage is not reduced by the transport's hardness, and is applied in addition to all damage caused by maneuvers, crash checks (and crashes), and other effects.
There are seven steps to chases, which are explained in broad strokes here and then in detail in the following sections. These seven steps continue in cycles until the chase ends - either with the crash or escape of one of the transports.
Turn Order[edit]
Chase Rules: Turn Order Details
Step 1: Choose Maneuvers[edit]
Each transport secretly writes down their intended manuver.
Step 2: Maneuver Checks[edit]
The pilots make an opposed maneuver check adding thier skill+transport handling.
Step 3: Spend Action Dice[edit]
Each pilot can adjust rolls or activate critical successes or failures by spending action dice.
Step 4: Resolve Maneuvers and Adjust Lead[edit]
The successful maneuver's effects are applied and the lead is adjusted.
Step 5: Lead and Obsticles[edit]
GM rolls for obsticles.
Step 6: Other Actions[edit]
Every occupant of the transports may perform one full action or two half actions. A pilot may perform one half action, for a -4 penalty to their next maneuver check.
Step 7: Crash Rolls (if any)[edit]
"Simpson, Hoooomer Simpson. He's about to hit a chestnuuuut treeeee. AAARRGHHHH!!!" ScrreeeeH CRASH!!!!
Maneuver Descriptions[edit]
Several elements go into the description of each maneuver. Following the maneuver name is a general statement of intent for the predator or prey. The DM may need to modify these basic concepts slightly to fit the particulars of each chase. This is followed by several entries for most maneuvers.
Lead
This describes the minimum or maximum distance between predator and prey required to perform the maneuver. Both predator and prey tend to have more options as the two transport become more closely entangled.
Speed
Succeed or fail, both predator and prey's maneuvers may temporary modify the current chase speed, In the case that both predator and prey choose maneuvers that alter the chase's speed, only the highest modifier (positive or negative) applies.
Success
This describes the effects of the maneuver, which applies when a pilot who chose it wins the opposed maneuver roll for the chase round.
Special
Maneuvers marked "Daredevil" stress a vehicle to the limit. PCs with the Daredevil ability are able to use these maneuvers more reliably and with less damage to their transports. Those marked "Daredevil Only" are so extreme that only PCs with the Daredevil ability may attempt them. The last maneuver in each category - "That's Impossible!" - may only be performed by an agent with the "That's Impossible!" ability.
Finishing maneuvers end the chase if performed successfully and have prerequisites that must be fulfilled before they can be attempted.
Actions During Chases[edit]
During chases, agents act in initiative order as usual, but many actions are restricted or illogical. The driver of a vehicle is limited to a single half action (at most) and thus is restricted from taking any full actions.
Initiative Actions During Chases
Initiative actions work normally during chases.
Attack Actions During Chases
A passenger in a moving vehicle suffers a -2 penalty to his attack rolls. This penalty is increased to -6 for the driver of the vehicle. Further, the driver and all passengers suffer an additional -2 penalty to their attack rolls for every 50 mph the vehicle is traveling (rounded down). Melee attacks may only be made if the prey's lead is 0 and/or the attacker is in or on the same vehicle as his target.
Movement Actions During Chases
Movement actions may be taken, but a Balance check is needed in most cases. A Jump check is required to leap between two moving vehicles. Finally, if an agent falls from a moving vehicle, he suffers normal falling damage (see page 236) using the speed of the vehicle (in MPH) as the distance of the fall. Thus, an agent who falls off a car traveling at 75 MPH takes damage as though he has fallen 75 ft.
Other Actions During Chases
Other actions may or may not be possible, and are subject to the Game Control's discretion. In general, only skills and feats that don't require movement remain unaffected.
Attacking Transports[edit]
Base attacks always hit transports unless a critical hit is rolled. You can attempt to ram a transport, the DC is the target's defense.
Transport Defense A transport's defense equals it's base defense added to the pilot's Dex modifier.
Critical Hits Against Vehicles
Critical hits on enclosed (Inside carrages) transports consult this table:
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Critical hits on open (Horses, etc.) transports consult this table:
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After you have rolled a hit location, consult the appropriate entry to determine the critical hit's effect.
- Motivation: This location refers to the transport's locomotion source (Horses, magic, elementals). Crits to this location negate the protection from the hardness rating. After the first motivation crit each crit that follows drops the transport's max speed by 10%. i.e. if a transport gets 4 motivation crits then it's max speed is minus 30%.
- Steering: Deduct damage as per normal. Additionally the transport's handling is -1 for every 10% of it's max HP.
- Wheels: Rather than the main transport being attacked this crit effects the individual wheels. Wheels can take 5hp of damage before they fall apart. In the event of tire breakage make an immediate crash check. The pilot takes -2 to his pilot roll for every trashed wheel up to a max total of -10. After that this crit is applied to steering.
- Weapon: If the transport has a weapon this crit attacks it. (see damaging objects in the PHB). If the transport has no weapons than this crit is applied to wheels.
- Window: This crit has found a chink in the transport's armor. The attack is randomly applied to one of the passengers (who is denied their dex bonus). Roll vs. the victim's defense, if the attack is unsuccessful then nothing happens.
Transport Damage[edit]
Roll damage for transports then minus cover and it's hardness. The remainder of damage is taken by the transport.
Transport Damage Checks[edit]
As transports take damage they get more broken! The following list details the modifiers the transport takes as it becomes more damaged:
There are four conditions a vehicle can be in after suffering damage.
Transport Okay: If the transport still has half its original HP, there are no modifiers.
Transport Crippled: After half of a transport's HP is gone its handling is reduced by 5. The pilot rolls a crash checkck with a +5 modifier to the DC.
Transport Disabled: Once the transport's HP hits 0, the chase ends. The pilot rolls a crash check at +10 to the DC.
Transport Destroyed: If a transport takes damage that's more than x2 it's max HP then the transport flys apart (or dies if it was alive) Roll damage for the passengers like a failed crash test. Passengers can attempt Jump or Roll checks (DC 20, +2 for every 25 MPH the transport was traveling) to half the damage they recieve.
Crash Checks[edit]
Crash checks should be made in four instances.
When the transport's wheel breaks up.
When the pilot scores a critical failure with his maneuver check.
When a successful maneuver calls for a crash check.
When damage to a transport calls for a crash check.
A crash check works like a maneuver check, but a pilot makes only one crash check per round. The base DC for a crash check is 15. If a pilot is required to make multiple crash checks in a round he instead makes a single check, adding 5 to the DC for every additional crash check the driver has been asked to make this round.
In addition, the following modifiers apply:
| Circumstance | DC Modifier |
| Open terran | -5 |
| Close terrain | +0 |
| Tight terrain | +5 |
| Every full 25 MPH of speed | +2 |
Whenever a pilot fails a crash check, his transport collides with the environment (or the other transport, if the successful maneuver calls for it). Damage to each transport (and occupant) equals Id6 for every 10 MPH of transport speed, +1 for every point by which the pilot failed his crash check.
Each occupant of the transport may make a Jump or Tumble check (DC equal to the failed crash check) to jump free of the transport, reducing the damage by half.
After the wreck, roll d%. If you roll over the speed (in MPH) the transport was traveling at the time of the wreck, then it is upright after the crash. If the transport survives the wreck with at least I wound point, then it still runs.
Repairing Damage to Transports[edit]
A PC with the appropreate skill may attempt to repair a damaged transport (or nurse it back to health if it is alive) if he has the proper parts and tools. At the end of every day of repair, the PC makes a check and consults the table below to see how many HP are restored to the vehicle. Repairs cost 1/50 the original value of the transport per day if you perform them - a professional demands 1/25 the original value of the vehicle per day to repair the damage.
A critical success with the check means that you automatically repair the maximum number of wound points possible according to the table rather than rolling for it (e.g. if you score a critical success with a check of 27, you repair 30 HP instead of 5d6).
A critical failure with a check not only fails to repair damage, it lowers the transport's maximum wound points by 1d6. If this reduces a transoprt to less than 1 wound point, it is irreparably destroyed.
Bystanders[edit]
Sometimes, the DM may determine that the chase terrain contains bystanders who can attack and be attacked by transports involved in the chase. This usually happens in close and tight terrain, where chases can take place in populated areas like town squares.
When attacking bystanders with a transport, the pilot uses his to make the attack, applying all attack modifiers that normally apply in chases. If he hits, he does 1d6 damage for every 10 MPH of his transport speed. Critical hits are applied to HP as normal.
Bystanders can target transports and their occupants as well, using the rules under Attacking Transports, above.
