Vehicle speed

The wiki lists vehicle speeds in units of pixels per day.

Walking

A character with an empty inventory travels at a speed of 10 units per day on any road type. Tiredness and damage have no effect on traveling speed (this is true for vehicles as well).

Vehicles

Each land vehicle or ship has a base speed and a load factor, which are listed on the vehicle's own wiki page.

The base speed determines the speed at which the vehicle moves, were there no load. A vehicle with a larger base speed will usually go faster than a vehicle with a smaller base speed. Base speeds of ships and land vehicles are not comparable, because the land vehicle's base speed must be multiplied by the road factor.

The load factor determines how sensitive a vehicle's speed is to the load on the vehicle. A vehicle with a larger load factor will not be slowed so much by a heavy load.

Road vehicles

Vehicle speeds are only affected by road type and load weight.

Vehicle speed = (base speed)*(road factor) - (load)/(load factor)

Effect of road type

Certain vehicles can only travel on improved roads - for example, the limousine can only travel on a sand road or better.

Most importantly, each level of improvement makes all vehicles (walking is unaffected) travel 20 to 30 percent faster.

A summary of the levels of road improvement can be found here

Water vehicles

Ship speed = (base speed) - (load / load factor)