GET UP, STAND UP, stand up for your bike.

Like in a Richard Scarry book, downtown Portland on a weekday afternoon bustles with many forms of transportation. Buses pass pedestrians who just got off the MAX, and taxis roll through stop signs while cars line up on Burnside.

Unlike a children's book utopia, however, not everyone's happy with all the ways to get around. Zipping through traffic, fixed-gear bikes, or "fixies," continue to be ticketed by Portland police for what the cops consider equipment violations.

The ongoing ticketing highlights the Legislature's recent failure to clear up legal ambiguities around the bikes, which are brought to a stop by the application of back pressure on the pedals instead of more common hand or coaster brakes. The legs of the cyclist, coupled with the bike's gearing, act as a brake.

Local bike advocacy lawyer Mark Ginsberg worked with Oregon legislators in the just-concluded session to fix matters with Senate Bill 729. That bill included a provision that said fixed-gear bicycles are "not required to be equipped with a separate brake."

"We just spent a lot of time in the Legislature, and we thought we had it clarified," says Ginsberg.

But the fixies clause in the larger bill dealing with bikes died in the Judiciary Conference Committee after Sen. Ginny Burdick (D-Southwest Portland) stripped it out. A local bike blog, bikeportland.org, reports that Burdick's daughter lobbied her not to green-light the surge of inexperienced fixie riders.

"After it initially went through, I had a lot of reservations," Burdick said in an interview with Jonathan Maus, editor of Bikeportland. "My own daughter (who works at River City Bicycles in Portland) rides fixies on the velodrome. She jumped on me pretty hard and said there were a lot of people on fixies who really don't know what they're doing, so changing the standard across the board would not be a good idea."

River City Bicycles sells one type of fixed-gear bicycle without brakes. All its other models come with brakes. Most bike shops in Portland that offer fixies, including Bike Gallery and Bike N' Hike, sell them with brakes.

Sleek and simple, fixies have become popular with everyone from couriers to a hipper sect of the bike commuter set. At the same time, some of these cyclists claim police, exploiting a vaguely written fixies provision left untouched by the Legislature, are targeting them.

"They're real selective about who they give tickets to," says Matthew Henry, 23, a bike messenger who has been ticketed five times for riding a "brakeless" bike. Citations cost $97 apiece.

"They're focusing on the messengers," says Tab Bamford, an independent bike courier. "And they're the ones who actually know how to ride these bikes."

Portland police estimate that they give anywhere between four and 10 citations a week for "bicycle equipment violations," the infraction given to fixed-gear bicycles not equipped with a standard brake. But police insist they do not target specific people.

"Most of these guys are messengers running from building to building downtown, and that's where I am," says Officer Bret Barnum, a motorcycle cop. "We're not out to target people."

Bamford, 30, has been a messenger for over six years and has twice won the North American Cycle Courier Championships, first in 2002 in Houston and then in 2003 in Washington, D.C. While he feels that messengers are being unfairly penalized, he realizes the bikes can be dangerous under the heels of the inexperienced. Without the proper strength, the bikes are hard to stop. Portland police say legs aren't brakes.

"In the interest of public safety, you do need a separate mechanism," says Barnum. He and Officer Bill Balzer, another Portland motorcycle cop, hand out over 90 percent of the citations in question. He says the way the law is written "leaves it open for interpretation" and that he reads the law as requiring "an independent mechanism that allows the bike to stop."

Not everyone, however, reads it that way. Currently, Oregon Revised Statutes 815.280(2)(a) says a bike "must be equipped with a brake that enables the operator to make the braked wheels skid on dry, level, clean pavement." On Jan. 1, SB 729 clarified the law a bit. Instead of skidding, cyclists must show they can stop within 15 feet going 10 mph.

"What does 'equipped' mean? What does 'brake' mean?" Ginsberg says. "Nowhere does it say you need a mechanical caliper brake."

State Sen. Jason Atkinson (R-Central Point), who worked closely with Ginsberg on SB 729 last session, raced bikes professionally for eight years before he "went through a windshield and went into politics."

"A large number of people don't understand how many fixies there are and how safe they are," says Atkinson, the original sponsor of the bill.

But Barnum disagrees, saying that it's "about safety for everybody."

"The silent majority have said, 'Hey, guys, put your brake on and you're good to go,'" he says. "The vocal minority are the same 20, 25 people who refuse to do this."