Anyone traveling Washington Avenue these days had better have quick reflexes and nerves of steel.

The right lane is nearly always blocked by something, and often the left one is as well, despite the street's role as a major connector between Columbus Boulevard and I-76. Trucks off-load crates of vegetables for the Italian Market. Cars line up to enter a popular Vietnamese shopping center at Sixth Street. Bicyclists mob the Mexican taco truck at 10th. Forklifts dart out from between the parked cars, shifting slabs of marble between building-supply stores on the west side. Triple parking is routine.

The chaos is both annoying and wonderful in equal measure, the mark of an ethnically and economically diverse commercial corridor. It's also extremely dangerous.

It has become almost impossible to make out the white stripes that once demarcated the Washington Avenue roadway. The absence of clear lines separating the warring parties - motorists, bicyclists, pedestrians, and delivery trucks - has only accentuated Philadelphians' natural inclination for roadway anarchy.

Four people have died on Washington Avenue in the last five years. Crashes resulting in serious injuries are now occurring almost once a week. Everyone who has anything to do with the street agrees the city needs to do something, and quick.

But restoring order is no simple paint job. To put down stripes, you need to know what kind of street you're striping for.

Street markings are typically designed to match their surroundings. Residential streets tend to have narrow lanes, generous buffers, and short signal intervals to force motorists to slow down. Through-streets get wider spaces and longer signals so the traffic can flow. Commercial streets need a bit of both approaches, plus generous lay-by lanes for pickups and loading.

Washington Avenue is all those streets rolled into one; that's what makes it one of Philadelphia's most exciting places. Yet, the mix seems to be changing before our eyes.

As the border neighborhoods fill up with new residents, the pressure to retrofit the heavily commercial avenue for pedestrians and bikers has intensified. Though you can't argue against safety, you have to wonder where those changes will leave the businesses, especially those that depend on daily visits from 18-wheelers.

At the western end, where contractors and architects once scoured a strip of showrooms for the perfect bathroom tile, you can now find an upscale bakery and child-care center. The Mexican population on the eastern end has grown so fast that Sacks Playground at Fifth Street now hosts back-to-back soccer games all weekend.

In the last year, a half-dozen developers have put in plans for new apartment buildings, including a 1,600-unit, 32-story megaproject from Bart Blatstein at the northeast corner of Broad. That has caused Point Breeze residents to worry the avenue's remaining industrial jobs will disappear. To appease everyone, the Planning Commission has been trying to come up with a new zoning plan for Washington Avenue. But it's months, if not years, down the road.

So, how do you stripe a street for a future that hasn't arrived yet?

Philadelphia officials hope to resolve that question in meetings with representatives of Washington Avenue's varied constituencies. This will be Restriping 2.0.

Two years ago, the Streets Department produced a detailed striping plan, tailored for the different zones along the avenue. It featured extra turning lanes in some sections, lane reductions in others.

Everyone hated it.

So when the Mayor's Department of Transportation and Utilities (MOTU for short) decided to start over, it invited all the stakeholders to participate in a joint conversation. The Bicycle Coalition was to sit down Thursday with the Washington Avenue Property Owners Association, which represents the building-supply stores, and the strangely named South 9th Street Businessmen's Association, which represents the market. Members of every neighborhood group, from Jefferson Square to Graduate Hospital, were also expected.

Judging from interviews with the stakeholders, MOTU has its work cut out for it.

While the Bicycle Coalition and residents groups talk about installing wider sidewalks and a center median to help pedestrians cross the 76-foot-wide avenue, merchants balk at the prospect of giving up the travel lanes to make those improvements possible.

"We don't want to reduce car counts," Tom Donatucci, who represents the owners of the building-supply showrooms on the west side, told me plainly. The showrooms have been hit hard by the likes of Home Depot and Lowes, located in sprawling shopping centers, and they worry they'll lose customers if the new traffic pattern makes it hard to cruise the avenue.

Michele Gambino, who represents the market vendors, sides with Donatucci's group, but she's more focused on creating dedicated loading zones. "Remember, our purveyors don't have back doors. We have to do business in the front, on the street," she explained.

And then there is everyone in between. The Vietnamese supermarkets at Sixth and 11th Streets. The Anvil Ornamental Iron Works at 10th, which still turns out much of the decorative wrought iron you see around Philadelphia. The loft apartments at 11th and Broad.

Clearly, there is room for increased residential density on the avenue, as Lauren Vidas, chair of the South of South Street Neighborhood Association, advocates. A wide street can handle tall buildings.

Yet there is more to a city than housing. Washington Avenue's gritty mix of commerce and manufacturing, a legacy of the days when a four-track freight railroad ran down the middle of the street, offers an alternative, as well as jobs. We have plenty of wide streets lined with housing - Broad Street, Spring Garden. But Washington Avenue's mash-up is uniquely un-Philadelphia, more like a Los Angeles boulevard. That eccentricity is worth protecting.

Then we can get back to bike lanes.