Paul Martinez has been riding motorcycles for more than 30 years.

For him, it is a bold, breathtaking way to see places in the beautiful backcountry of San Diego and Riverside counties - places such as cool, heavily forested Palomar Mountain.

Like many motorcycle riders, the Oceanside man splits lanes now and then en route to his destination. He says he is careful about when and where.

"I split lanes when traffic is stalled," Martinez said by e-mail recently. "But I do it at about 20 mph or slower, to give myself time to react."

Martinez suggests that lane splitting is dangerous when traffic reaches 30 mph. He is amazed by how many riders squeeze past cars and trucks when traffic is moving at 70 mph or greater.

"Do these riders think they are invincible?" Martinez asked. "If a car changes lanes without seeing them, they're history."

It's probably a good idea to follow Martinez's guidelines. But, as it turns out, there are no hard and fast rules.

There is an impression among many that California law allows lane splitting in bumper-to-bumper, rush-hour conditions and bars the practice in free-flowing traffic. That's apparently not the case.

California Highway Patrol Officer Ron Thatcher in Temecula said in a telephone interview Friday that the law specifies only that the practice is legal. It does not set specific limits.

"So basically, what we go by is being safe and prudent in passing," Thatcher said. "Throughout my 20-year career, I have used a 10 mph rule."

In other words, he said, a safe pass is one where a motorcycle travels no more than 10 mph faster than traffic.

Contrary to what some think, Ken Harrison, owner of the Oceanside-based California Comedy Traffic Schools, said the law's origin has nothing to do with giving agile motorcycle commuters a way to thread through traffic jams.

The origin goes back to a time many years ago when most cycles were air-cooled and "the engines would just burn out if they didn't keep moving," he said.

A lot of trapped, car-bound commuters resent the fact that motorcycles can zip by while they slug along at 10 mph, Harrison said. But he said those commuters should remember that the privilege comes with a significant risk.

"You can walk away from a 60 mph collision in a car, but you can't do that on a motorcycle," Harrison said. "Motorcyclists are a lot like airplane pilots: They either walk away from an accident or they are dead."

Clearly, it's crucial for drivers and riders to look out for each other.

- Readers are encouraged to ask questions and submit ideas for commuter columns. Staff writer Dave Downey may be reached at (760) 740-5442 or ddowney@nctimes.com. For the latest traffic conditions, or to comment on this column, go to nctimes.com.