Source GM Core pg. 36

Depending on how you track movement, the adventuring party might track the overland distance they travel in feet or miles based on the characters' Speed with the relevant movement type. Typical rates are shown on the Travel Speed table. Groups traveling in vehicles instead use their vehicle's Speed, as noted in that vehicle's entry.

The rates on the Travel Speed table assume that the characters are traveling over flat and clear terrain at a determined pace, but one that's not exhausting. Moving through difficult terrain halves the listed movement rate. Greater difficult terrain reduces the distance traveled to one-third the listed amount. If the travel requires a skill check to accomplish, such as mountain climbing or swimming, you might call for a check once per hour, referencing the resulting distance on the Travel Speed table to determine the group's progress.

Travel Speed