This article is from the Lure Coursing FAQ, by Bonnie Dalzell with numerous contributions by others.
The unentered dogs cannot be allowed to run loose during the trial.
Allowing small fluffy dogs that resemble lures to run loose on the
coursing field is inadvisable. Hounds that wish to run but are not
allowed to run may be quite frustrated.
It is important to always have adequate control over dogs that are not
actually participating in the course in progress. There is a fine for
having a loose dog interfere with a course in progress. Novices with
retired racing greyhounds frequently have to pay this fine as the
hounds suddenly show much more excitement than the owner has ever seen
up until that time (that is they go berserk with happiness and
Sighthounds have thick muscular necks and slender heads and can easily
and unexpectedly slip a buckle collar when they become excited at the
sight of the moving lure with other hounds in pursuit. For this reason
you should have a martingale or choke collar for restraint of the
hound at the trial site.
It is relatively common for dogs brought to the trial site and left
loose in a car to become excited at the sight and sound of the lure
and destroy part of the car's interior. Rear view mirrors and
upholstery are favorite targets. If the windows are left partially
rolled down the dog may injure itself as it tries to get out through
the window. Crating or tethering the dog with a tie out that it cannot
chew through prevents these problems. Obviously no one should leave a
dog alone in an unshaded car in hot weather.