Armed rangers patrol the riding area at Oceano Dunes in pickup trucks, on all-terrain vehicles and even in a souped-up dune buggy called a sand rail.
But park managers have a secret weapon that is far less macho and high tech.
Every weekend a small army of volunteers fans out through the park, each member wearing a khaki vest that identifies them as a park official.
Their favorite vehicle is a lumbering six-wheeled golf cart called a Polaris, which can barely reach 25 miles per hour but never gets stuck in the sand.
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Their mission is to stop anyone they see doing anything unsafe, illegal or otherwise stupid and remind them of the park's many rules and regulations.
"I'm your 'get out of jail free' card," said volunteer patroller Chris Cannon. "I'm the guy who warns people who are doing something wrong before they have to deal with a ranger with a badge and a gun."
The volunteer program began in 2002 and has since grown to some three dozen members, said Superintendent Andy Zilke.
Unlike rangers, volunteer patrollers are not armed, making them less intimidating.
"These are OHV enthusiasts talking to OHV enthusiasts," Zilke said, adding that they "get a really good response."
– David Sneed