Vehicles
From chariot races to pirate ship attacks to airship journeys, countless adventures take place atop speeding vehicles. All vehicles have the following properties:

Terrain: Vehicles fall into three terrain categories: land vehicles, water vehicles, and air vehicles. Vehicles travel in the terrain of their category. Proficiency with a category of vehicles allows a creature to add its proficiency bonus to any checks made regarding that type of vehicle. 

Size and Armor Class: Just like creatures, vehicles have size categories and each has an AC that determines how difficult it is to hit with attacks.

Hit Points: When a vehicle is reduced to 0 or fewer hit points it is destroyed. In addition, when a vehicle is reduced to 50% of its total hit points, it suffers a malfunction and must roll on Table: Malfunction.

Speed: Vehicles are listed with their movement speed, as well as their journey speed for traveling long distances.

Crew: Many vehicles only require a single crewman as a driver, but larger vehicles may require even dozens of people to properly operate. Drivers cannot perform actions using a vehicle unless the minimum crew requirement is met.

Immunities: As objects, vehicles are immune to poison and psychic damage. They are also immune to the blinded, charmed, confused, deafened, fatigued, frightened, incapacitated, paralyzed, petrified, poisoned, prone, slowed, strife, stunned, and unconscious conditions, as well as any other effect that would result from failing a Wisdom, Intelligence, or Charisma saving throw. 

Havens: A vehicle acts as a haven if it provides accommodation and shelter from the elements. Sometimes, the environment may not be suitable for it to act as a haven.

Driving
Unlike creatures, all vehicles have a “front”, in many situations, this facing will dictate the way the vehicle moves.

In order to move, all vehicles require a driver. While at the steering (such as the reins of a wagon or the wheel of a ship) a creature can use a bonus action to make the vehicle perform one of the following actions:

Drive: The vehicle moves half of its movement speed directly forward, then the driver may change the vehicle’s facing by up to 90 degrees (a full turn left or right) before moving up to the remaining movement speed. The vehicle gains momentum.

Maneuver: The vehicle moves half of its movement speed forward, and the driver may change the vehicle’s facing by up to 90 degrees (a full turn left or right) up to 2 times during this movement. This action cannot be performed while the vehicle has momentum.

Ahead Full: The vehicle moves one and a half times its movement speed directly forward. The vehicle gains momentum. If the vehicle would roll for a malfunction before it is used to take another action, it rolls twice on that table instead (reroll any duplicate results).

Brake: The vehicle moves half of its movement speed directly forward, then it loses momentum.

Momentum. At the initiative count of 20, all vehicles with momentum move half their movement speed directly forward. Momentum ends automatically after 1 minute if no actions with a vehicle are taken.

Saving Throws. Unlike most objects, vehicles must make Strength, Dexterity, and Constitution saving throws as if they were creatures against effects that would call for them. All vehicles have a Strength and Constitution score based on their size (see below). A driven vehicle has a Dexterity score equal to its driver’s Dexterity score (a vehicle without a driver has a Dexterity of 0).

Size
The size of a vehicle determines many of a vehicle’s properties:

Strength, Constitution, and Carrying Capacity. A vehicle’s Strength, Constitution, and carrying capacity are determined by its size.

Large: A Large vehicle has a Strength and Constitution score of 14 (+2), can carry up to 3 passengers along with the driver, up to 40 Supply, and up to 10 bulky items in addition to 2,000 lbs. of carrying capacity.

Huge: A Huge vehicle has a Strength and Constitution score of 18 (+4), can carry up to 6 passengers along with the driver, up to 80 Supply, and up to 20 bulky items in addition to 4,000 lbs. of carrying capacity.

Gargantuan: A Gargantuan vehicle has a Strength and Constitution score of 22 (+6), can carry a number of additional passengers equal to the minimum required crew, up to 800 Supply, and up to 200 bulky items in addition to 40,000 lbs. of carrying capacity.

Collisions. If a vehicle has momentum and enters the space occupied by a creature or another object, a collision occurs. Both the vehicle and whatever it impacts take damage according to the vehicle’s size: Large—4d6 bludgeoning damage, Huge—8d6 bludgeoning damage, Gargantuan—12d6 bludgeoning damage.

If the object or creature impacted is the same size as the vehicle or larger, the vehicle immediately stops and loses momentum. If the object or creature impacted is smaller than the vehicle, it is shunted into the closest unoccupied space that allows the vehicle to complete its movement unimpeded.

Malfunctions
When a vehicle is reduced to half its total hit points or less, roll 1d6 on Table: Malfunctions to determine what aspect of the vehicle is breaking. Vehicle malfunctions are usually too extreme to repair quickly except by magical means and remain until the vehicle’s hit points are restored to their maximum.

Malfunctions (1d6)

1. Movement. Movement has been compromised, such as losing the sails, losing the animal team drawing the vehicle, or destroying an engine. The Drive, Maneuver, and Ahead Full actions cannot be taken until it is repaired.
2. Integrity. Some key component holding everything together has been lost and the vehicle immediately loses an additional 25% of its hit point maximum.
3. Brakes. The ability to stop has been lost. The Brake action cannot be taken until repaired. 
4. Steering. The driver’s ability to fully control the vehicle has been compromised. The Drive and Maneuver actions cannot be taken until repaired.
5. Cargo. Half of any Supply currently carried by the vehicle is destroyed.
6. Superficial. The damage looks bad but doesn’t cause any further issues.

Repairing Vehicles
Repairing damaged or malfunctioning vehicles requires a tool check against the DC listed for the vehicle's primary material as shown on the Materials table. During a long rest, you can make one check, ending any malfunctions it currently has on a success and restoring hit points equal to the result of your check. Alternatively, you can hire someone to repair your vehicle for you (which is an automatic success and typically costs 1/5th of the vehicle's total cost).

Special Features
There are any number of fantastical possibilities when it comes to vehicles but the following features are the most common:

Armed. Armed vehicles have one or more weapons in place on board (see Table: Siege Weaponry). A creature can use an action to fire a siege weapon or use an action to reload it.

Drawn. A drawn vehicle is pulled by one or more beasts of burden and its movement and travel speeds are determined by the animal (or animals) pulling it.

Personal. Personal vehicles are designed for a single occupant and usually have far less space. Vehicles with this property can only ever carry a maximum of one person and have half as much carrying capacity as normal for a vehicle of the same size.

Three-Dimensional. A three-dimensional vehicle may also turn up or down when making turns.

Transport. Transport vehicles are designed for cargo and crew, and have 1/4th the carrying capacity of a normal vehicle of the same size.

Table: Land Vehicles

Table: Water Vehicles

Table: Air Vehicles

Table: Siege Weaponry

*This siege weapon cannot attack targets within 60 feet.