The rules on travel pace in the Player’s Handbook assume that a group of travelers adopts a pace that, over time, is unaffected by the individual members’ walking speeds. The difference between walking speeds can be significant during combat, but during an overland journey, the difference vanishes as travelers pause to catch their breath, the faster ones wait for the slower ones, and one traveler’s quickness is matched by another traveler’s endurance.
A character bestride a phantom steed, soaring through the air on a carpet of flying, or riding a sailboat or a steam-powered gnomish contraption doesn’t travel at a normal rate, since the magic, engine, or wind doesn’t tire the way a creature does and the air doesn’t contain the types of obstructions found on land. When a creature is traveling with a flying speed or with a speed granted by magic, an engine, or a natural force (such as wind or a water current), translate that speed into travel rates using the following rules:
For example, a character under the effect of a wind walk spell gains a flying speed of 300 feet. In 1 minute, the character can move 3,000 feet at a normal pace, 4,000 feet at a fast pace, or 2,000 feet at a slow pace. The character can also cover 20, 30, or 40 miles in an hour. The spell lasts for 8 hours, allowing the character to travel 160, 240, or 320 miles in a day.
Similarly, a phantom steed spell creates a magical mount with a speed of 100 feet that doesn’t tire like a real horse. A character on a phantom steed can cover 1,000 feet in 1 minute at a normal pace, 1,333 feet at a fast pace, or 666 feet at a slow pace. In 1 hour, the character can travel 7, 10, or 13 miles.
When traveling outdoors, characters can see about 2 miles in any direction on a clear day, or until the point where trees, hills, or other obstructions block their view. Rain normally cuts maximum visibility down to 1 mile, and fog can cut it down to between 100 and 300 feet.
On a clear day, the characters can see 40 miles if they are atop a mountain or a tall hill, or are otherwise able to look down on the area around them from a height.
While exploring, characters might encounter other creatures. An important question in such a situation is who notices whom.
Indoors, whether the sides can see one another usually depends on the configuration of rooms and passageways. Vision might also be limited by light sources. Outdoor visibility can be hampered by terrain, weather, and time of day. Creatures can be more likely to hear one another before they see anything.
If neither side is being stealthy, creatures automatically notice each other once they are within sight or hearing range of one another. Otherwise, compare the Dexterity (Stealth) check results of the creatures in the group that is hiding with the passive Wisdom (Perception) scores of the other group, as explained in the Player’s Handbook.