Size, Space, and Capacity
Source GM Core pg. 234
Vehicles have size traits, but they don't occupy the same spaces that most creatures use. Instead, each vehicle has specific dimensions provided in its stat block. The sizes given are for Medium humanoid creatures, and creatures with different shapes and sizes might need vehicles that are differently sized. Buying vehicles for Tiny, Small, or Large creatures rarely impacts the consumer price of the vehicle.
Most vehicles are Large or larger, and many are made for the purpose of carrying cargo. Unless stated otherwise, the amount of cargo a vehicle can carry depends on its size, terrain, and propulsion. Most land transportation can haul around 500 Bulk of goods, while pulled vehicles can typically hold 100 Bulk per Large creature pulling. Water vehicles, such as a ship, have limits that are more based on volume than weight; a ship can hold upward of 1,500 Bulk. Flying vehicles can typically hold only 1/10 the Bulk of a water vehicle and still remain airborne. The GM might rule that unique or unusual vehicles can hold different amounts of Bulk.
Most vehicles are Large or larger, and many are made for the purpose of carrying cargo. Unless stated otherwise, the amount of cargo a vehicle can carry depends on its size, terrain, and propulsion. Most land transportation can haul around 500 Bulk of goods, while pulled vehicles can typically hold 100 Bulk per Large creature pulling. Water vehicles, such as a ship, have limits that are more based on volume than weight; a ship can hold upward of 1,500 Bulk. Flying vehicles can typically hold only 1/10 the Bulk of a water vehicle and still remain airborne. The GM might rule that unique or unusual vehicles can hold different amounts of Bulk.