The following systems are based on the optional vehicle chase rules in the Call of Cthulhu, 5.5 edition rulebook, the armored vehicle rules in Fearful Passages, and the aerial combat rules written by Bob Kindel that appeared in Walker in the Wastes.

All ground vehicles have the following stats:

• MOVE: the maximum number of units the vehicle can move in a combat round. The MOVE stat is calculated by the formula X miles per hour x 0.8 = Move Y (round fractions up). So human beings have a MOVE of 8 based on an average speed of 10 miles per hour based on an average maximum speed of 6 minutes to a mile, where one round is three seconds long. This formula does not work for supernatural beings moving at extreme speeds (ie. Yog-Sothoth is able to fly hundreds or thousands of miles per hour, yet its MOVE of 100 has a maximum of 166 mph). In such instances, the game decision is up to the Keeper, and a good general rule is that any supernatural creature whose MOVE is more than 100 can move at any speed it wishes, and cannot be outrun except through supernatural means.

• HANDLING: a modifier to the Drive Auto or Operate Heavy Machinery skill based on how maneuverable the vehicle handles when a skill check is required. This skill check is further modified by the conditions in the Drive Roll Modifiers Table on p.250 of the Call of Cthulhu, 5.5 edition, as well as the following:

  MANEUVER	MODIFIER
  Speed of MOVE 9 or less	+10%
  Congested city street; minor debris on the road	-10%
  Bumper-to-bumper traffic; major debris on the road	-20%
  Bootlegger Reverse Success sets the vehicle in a skid which concludes with the vehicle facing in the opposite direction and can begin moving forward in the next round at half-speed. Cannot be performed with horse-drawn vehicles or heavy machinery (ie. tanks).	-25%
  Sharp Brake Success allows the vehicle to decelerate to a stop at twice the ACCEL/DECEL score the vehicle would have in a normal stop. Failure decelerates the vehilce at the standard ACCEL/DECEL score and requires a roll on the VEHICLE TROUBLE TABLE.	-20%

• ACCEL/DECEL: how many MOVE units the vehicle can accelerate or decelerate to in a single combat round. A vehicle may decelerate at twice the ACCEL/DECEL by making the Sharp Brake manuever (see above).

• HP: the total number of hit points the vehicle can take damage to before being rendered inoperable.

• ARMOR: the amount subtracted from hit points of damage taken by both the vehicle and its occupants. Armor is calculated by thickness in millimeters multiplied by 2 (ie. 5mm of armor = Armor 10).

• SIZE: same as the characteristic SIZ, averaging height, weight, and volume into a single number.

Driving under normal conditions does not require a skill check, but driving under these conditions do:

• Driving through bad roads in rough weather
• Driving while under attack
• Driving while chasing or being chased by another vehicle or creature
• Driving without the requisite skill in that type of vehicle (at least 20% skill)

VEHICLE TROUBLE TABLE
d12	AUTOMOBILE TRUCK	MOTORCYCLE	HEAVY VEHICLE*	HORSEDRAWN VEHICLE**
1	Flat Tire	Leaking Tire	Loose Tread	Cracked Wheel
2	Engine Trouble			Broken Harness
3	Engine Damage			Broken Axle
4-6	Skid
7	Fishtail
8	Severe Fishtail
9	Loss of Control
10	Crash
11	Rollover		Crash	Rollover; Lame Animal
12	Rollover; Engine Fire		Crash	Rollover; Lame Animal
* ie. tanks, halftracks, armored fighting vehicles ** this includes all vehicles drawn by an animal

Flat Tire/Leaking Tire/Loose Tread/Cracked Wheel: Vehicle is slowed to ¼ MOVE until repaired.

Engine Trouble/Broken Harness: Vehicle speed slows at maximum DECEL to zero until repaired by successful Mechanical Repair roll.

Engine Damage/Broken Axle: Vehicle inoperable until repaired by successful Mechanical Repair roll at half-skill.

Skid: Drive skill -20% in next round.

Fishtail: Drive skill -10% in next round

Severe Fishtail: Drive skill -15% in next round; roll on table again and add 2 to result.

Loss of Control: Drive skill -30% in next round; roll on table again and add 4 to result

Crash: If the vehicle was travelling at more than 30mph, have each passenger roll against Luck (motorcyclists at ½ Luck); failure results in that character being thrown from the vehicle (if the character is wearing a seatbelt or is in any other situation that makes being thrown from the vehicle unlikely, disregard the roll). For every 10mph the vehicle is travelling, roll 1d6 damage to each passenger thrown from the vehicle. Those passengers sitting or hanging on the outside of the vehicle must either make a successful Jump roll or suffer 1d6 damage per 10mph the vehicle was travelling. Damage done to the vehicle and the passengers inside is calculated by the VEHICLE COLLISION TABLE:

VEHICLE COLLISION TABLE
MOV	DAMAGE TO VEHICLE		DAMAGE TO OBJECT HIT
	SOLID OBJECT	SOFT OBJECT
0-4	none	none	none
5-12	1d4	none	1d4
13-20	1d4+1d6	1d4	1d4+1d6
21-28	1d4+2d6	1d4	1d4+2d6
29-36	1d4+3d6	1d4	1d4+3d6
37-44	1d4+4d6	1d4	1d4+4d6
45-52	1d4+5d6	1d4	1d4+5d6
53-60	1d4+6d6	1d4	1d4+6d6

Solid objects are stone or metal, while soft objects are made of flesh. A collision counts as an attack against all components on a vehicle, so that if the damage done exceeds any Armor the vehicle might have, the components will each take that amount of damage from the crash. Due to their tough shells, armored fighting vehicles take only half of collision damage.

EXAMPLE: The characters are speeding away from the Gestapo in an automobile when they crash head-on into a wall. The automobile was travelling at MOV 40 (50mph) when it struck the wall, which as a solid object does 1d4+4d6 damage to the vehicle. The Keeper rolls a total of 18 points of damage - the headlamps, suspension, fuel tank, radiator, tires, brakes, and steering are all totaled, but the engine survives. The occupants all take damage as well.

Rollover: The passengers are trapped in the wreckage and must make a roll against STRx5 to free themselves.

Lame Animal: Whatever animals were pulling the vehicle have broken their legs and can no longer pull a vehicle.

Engine Fire: Those passengers inside the vehicle take 1d6+2 fire damage per round, and roll on the VEHICLE FIRE TABLE in the Vehicle Ground Combat Rules section.

GROUND VEHICLE CHASE RULES
Unless miniatures are being used, the Keeper will state the distance in MOVE units between the chaser(s) and chasee. The chase will then follow this procedure:

1. Driver with the highest DEX goes first.
2. Accelerate (MOVE+ACCEL) to close/expand the distance between vehicles.
3. Roll skill check with requisite modifiers.
4. Roll Spot Hidden to identify any hidden obstacles.
5. Deal with any hidden obstacles on a failed Spot Hidden by rolling a Drive skill check to avoid hitting the obstacle.
6. If within range, the player may attack, ram, or cut in front of the other vehicle.
7. The driver with the next highest DEX acts, and so on...

The hidden obstacles are at the Keeper's leisure. There might be a pedestrian walking into the road, cars joining traffic, or no hidden obstacles at all. This is simply a device to throw in extra thrills.

Attacks and ramming are covered under the Ground Vehicle Combat Rules. Another manuever may be to drive your vehicle in front of a fleeing vehicle to prevent its escape. To accomplish this simply requires having accelerate (step 2) in front of the fleeing vehicle. This is useful to stop a vehicle without injuring the occupants, but it also allows the fleeing vehicle to make an automatically successful ram against you.