There are a few dog owners who want the run of things, but most dog owners realize that fences are to everybody's benefit. They keep dogs from getting smushed by cars, and keep owners from the ire of parents and others.

The numerous cities around the USA that have established and maintained dog parks have evidence that dog parks are as safe as other forms of popular recreation. None of those cities (that we have found) have needed special insurance or any kind of monitoring or watching. Nobody has been sued. Dogs seem to not be spreading diseases among themselves. Dogs have not been injured by other dogs --- although there are occasional instances of over-excited dogs running headlong into equipment and fences.

Dog experts attest that dogs that are inherently protective of their "own" property, such as their own house or yard, usually don't adopt a protective attitude when in "neutral" territory. Parks seem to qualify as neutral territory.

The issue of public liability has been resolved at other parks by the posting of signs that warn park users that they are entering an off-leash dog area, that they do so at their own risk, and that dog owners remain liable for their pets' behavior.

There are no guarantees, of course, just as there are no guarantees at a playground that none of the kids have something contagious. Or that the kids aren't going to get into a fight. Or that one of the kids isn't carrying a knife.