Off-Road Warriors : Population growth, Fitness Craze Fuel Crowding on Trails and Boardwalks.

Even on a beautiful weekend afternoon,there is no relief for road-weary Angelenos.

You get cut off. Some jerk crowds you from the right and another stops suddenly and blocks traffic on the left. And then some nut comes whizzing by from out of nowhere and scares you half to death.

With some luck you get back home or to the parking lot.

It’s hell out there on the region’s hiking, biking and riding trails.

The crowds are bigger, faster and, according to some critics, less courteous than ever. Even plain old pedestrians are having trouble coping with the increasing competition for space on the recreational byways of Southern California these days.

Population growth, the fitness craze and the advent of fast skates and mountain bikes able to go just about anywhere are making beach boardwalks, mountain trails and bike trails crowded, tense and increasingly dangerous.

About half the first-aid calls handled by Los Angeles County lifeguards are for injuries on busy seaside bike paths.

“There’s way more people these days and tempers are shorter than they used to be,” said county lifeguard Rodney Williams.

“A simple let’s-get-away-from-it-all trip to the woods,” said Sierra Club official Larry Frielich, “is becoming too much like real life.”

Or worse. When trail-running, in the Santa Monica Mountains, L.A. Roadrunners Coach Pat Connelly says, “I’ll send a scout up ahead to look for mountain bikers. It’s like a military operation.”

It’s enough to make you want to go out for a drive.

Or just stay at home, which is how thousands of Southern Californians are choosing to deal with the crowded conditions and increased tensions, officials say.

The region’s beautiful and accessible mountain and beach trails have fallen victim to their own popularity. As Yogi Berra once said of a restaurant: “It’s so crowded, no one goes there anymore.”

“Some of my friends just won’t come out [to the beach bikeways] because it’s so crowded,” said in-line skater Ethan Paritzky, who now practices alone on the strand in Venice. “I only come on weekdays. Weekends are a nightmare.”

While some sportsmen and women are giving up, others choose to just move farther down the line.

“We’ll go 20 miles to get the space we need,” said Connelly of the Roadrunners Club, whose students regularly drive from the Westside to Ventura County just to get some open road.

The situation is just as bad for cyclists. “We avoid the bike paths at all costs,” said Jim Burque of the Los Angeles Wheelmen Bicycle Club. “They are unusable, dangerous . . . much worse than heavy [road] traffic. At least in traffic you know where everybody’s going. “

In the mountains, tempers are flaring among equestrians, hikers and bikers, who are all seeking very different experiences from the same limited turf.

Hikers are seeking serenity, while the bikers are out for the thrill and a workout. The equestrians want to enjoy time with their animals, without being constantly spooked.

Officials are attempting to regulate recreational traffic. Bikes have been banned from equestrian trails in at least two Palos Verdes Peninsula towns and stricter regulations now limit their access to hundreds of miles of trails in state and national parks.

Some legal authorities are debating whether in-line skaters should be considered “vehicles” and be required to obey traffic rules as bicyclists are.

And there is constant talk among park officials, lifeguards, rangers and sports practitionersof other ways to police the diverse flow of recreational traffic.

At the core of the problem is the fact that there are 15 million inhabitants of Southern California, and they are increasingly turning to the outdoors for fitness and fun and in more varied ways than ever.

Mountain bikes were a novelty 10 years ago; now, bikers often outnumber hikers, rangers say.

Bikers complain about slow and erratic pedestrians in their way. Joggers hate bikers whizzing by within inches. And they all seem to dislike skaters.

There is also little respect for the simple Sunday stroller.

“The rule of thumb is that pedestrians will do the stupidest thing possible,” said in-line skating instructor Dave Inman. “They walk in big clumps, four abreast, oblivious to everything around them.”

The answer, most agree, is the same as for most man-made dilemmas: We need a little more common courtesy.

“There’s really only one rule necessary,” said Ross Blasman, a mountain biker who has worked to sooth tensions in the mountains. “Be considerate.”

While it’s hard to argue with the need for civility, the issue has grown beyond that. “Because it’s become a political issue, something that should be simple has become a nightmare,” Blasman said.

It’s a cycle: Renegade mountain bikers annoy hikers, who put pressure on park authorities to close trails to bikers. That concentrates riders into smaller areas, making hikers on those trails feel even more outnumbered.

“Then the hikers yell at the bikers: ‘Hey, you shouldn’t be on the trail,’ ” said Ted DePass, president of the Trails Council. And the bikers respond predictably to the challenge. “The same thing happens on our streets,” laments DePass. “It’s survival of the fittest.”