These rules are based off the Chase rules in Vornheim.
Anyway, before you have a chase you need vehicles right? For these rules, I assume we are talking things that move around the same speed, confined in some way to the ground and are much faster then people. I'm going to call them cars for the sake of convenience. Cars have 5 Stats; Speed, Handling, Armor Class, Hit Points and Dependability.
Speed and Handling are always modifiers added to the two types of rolls during a chase (Expounded upon below) Armor Class and Hit Points are the same as they are anywhere else in the game. Dependability is more or less a Car's catch all saving throw, except you generally want to roll beneath your dependability.
Your basic Car has the following stats;
AC: 12 (Or 8, in a descending AC system)
This is for a very bland car that can hold four people, or an roughly equivalent amount of people are cargo.
Here are a handful of other Cars for examples;
Old Jalopy you know like the back of your Hand
Law Enforcement Vehicle
So on and so forth. I was assigning stats at whim based on what made sense to me. I figure you can make a lot of vehicles based on your instinct this way - Motorcycles would have low HP and less cargo, for example. Cars should cost enough that low level characters can't afford them without a lone and high level ones can buy them without an thought; I think something equivalent to 500 standard Gold pieces would work. Price can be adjusted for especially bad (or good) cars.
On to the actual rules!
You have those being chased and the ones pursuing. Every round the driver of the chased vehicle must declare whether they are trying to outrun (Sudden acceleration, pedal to the metal, etc) the pursuer, or outmaneuver them (Sudden Breaking, a feint and a turn, etc.)
Then the chased party rolls a d10 and adds their dexterity score as well as either their Car's Speed modifier or Handling modifier (The former is applied to attempts to outrun, the latter to outmaneuvering them).
Whoever rolls lower loses an amount of "spaces" between them and the other Car. This means if the Pursuer wins, they move that many spaces towards the chased Car, whereas the opposite is true if the chased party rolls higher. Spaces are an abstract measurement that can really be anything - We used squares on a battle mat, but it could just as easily be inches on a table top or notches on a piece of paper. If the Pursuer not only manages to win the roll but also manages to overtake the chased car, they may attempt to ram them.
A ramming maneuver is a dangerous but effective way to damage the pursued car. The ramming car does 2d6 damage to the pursued car as well as their own, doing an additional 1d6 damage for every point they manage to overtake them by. The chaser can opt to do less dice worth of damage if they wish, but these must be taken away before damage is rolled.
If either party rolls a 10 or a 1, some unforeseen obstacle pops up that both drivers need to make dexterity checks to avoid. Hitting the obstacle should always have some form of immediate consequences, such as collision damage or civilian casualties. Examples obstacles include
- A line of schoolchildren
- An Apple Cart
- A sharp turn right in front of a shop of some kind
- A little old lady walking down the street
- A local law enforcement officer's vehicle
- A statue of a beloved public or religious figure
The passengers in either car may attempt to do anything they normally could. Most of the time this will be attempting to damage or disable the vehicles involved. If they are trying something unsafe and something bad happens to the car (Such as a collision) a reflex save or equivalent check needs to be made to prevent them from being thrown from the vehicle. All missile attacks receive a -2 penalty when being fired from a moving vehicle.
If a car takes more then half its hit points in damage, a Dependability check needs to be made. If this is failed, the car has been disabled in some way related to the nature of the damage; a crash may snap the axle, bullets could destroy a tire or something like that. If a natural 20 is rolled, the inhabitants need to move - not only is this car disabled, its going to explode in action movie pyrotechnics in 1d4 rounds! The explosion does 6d6 points of damage, half of that if you can manage a saving throw. A disabled car needs to be repaired before it will work again.
Certain spells, maneuvers or effects may also prompt Dependability checks based on the campaign setting.
A couple of final notes;
- Accidental collisions do 4d6 points of damage. Anyone inside the car takes a third of the damage done, half of it if they are not buckled in and they fail a reflex style saving throw.
- If a car reaches 0 hit points or below, it is automatically disabled. It must then make a dependability roll; if that is failed the car explodes as noted above.
Obviously this all goes on in till the pursued gets away or caught - or if everyone gets blown up.
I also had one last system going on. I used something like this to randomly generate the streets of the city as the chase went on. This gave the group more choices (Going left or right, for example) as well as unexpected obstacles (Dead end!) and I highly recommend it.