Travel restrictions allow you to specify the maximum distance you are willing to travel.
To enable a travel restriction:
click your name in the upper right corner of the screen, then
Next to Travel Restriction, click Edit
Enter your home address
Enter the maximum distance you are willing to travel
Travel restrictions are calculated on a straight-line distance (e.g. a 30 mile travel restriction will allow games within a 30 mile radius of the official's home address).