Besides being a busy commercial strip, a popular commuter route, and the boundary between Philadelphia and Lower Merion, City Avenue is a living, breathing, controlled experiment on how clashing policies affect two hoary American tribes - city-dwellers and suburbanites.

The Philadelphia side of City Avenue bubbles with an improvised stew of high-rise apartments, chain restaurants, college buildings, gas stations, and low-rent stores. Single-file lines of pedestrians course along the city's narrow sidewalk, forming clots around the bus stops. The Lower Merion side, by contrast, is dominated by an orderly, dots-and-dashes progression of mid-rise offices and surface parking lots. Human beings rarely appear anywhere near the curb on its equally skimpy footpath.

In the 1970s, the stretch of City Avenue located just west of the Interstate 76 interchange was known as the Golden Mile for Lower Merion's gleaming collection of corporate headquarters, which were drawn there by its low tax rate and easy access to Philadelphia. But the luster has dulled. Decline has set in. And it's visibly worse on the suburban side.

Philadelphia and Lower Merion have been jointly trying to right the situation, working through the regional authority of the City Ave Special Services District, to rezone the road. Philadelphia has already adopted changes aimed at nudging City Avenue in a more urban direction, with wider sidewalks, fewer parking lots, and more-welcoming facades. Now it's Lower Merion's turn.

The goal is nothing less than the reengineering of an auto-dependent commercial strip into a walkable, urbane street of apartments, offices, and shops. While there are thousands of strips like City Avenue riddling the American landscape, surprisingly few have been reincarnated as true city boulevards. It's not clear that such an ambitious transformation is possible. But if it is, City Avenue is a perfect candidate.

City Avenue differs from the typical highway strip in that it has many qualities we associate with urban places, including distinctive and relatively dense neighborhoods on both sides. There may be fewer pedestrians on the suburban edge of City Avenue - where multistory apartment houses are currently prohibited - but a culture of walking and commuting definitely exists. About 25,000 people work in the area between the expressway and East Wynnewood Road, and probably 40,000 more live within a 10-minute stroll.

City Avenue also is amply provisioned with transit, two train stations and six bus routes. In 15 minutes, you can be transported to Center City (assuming expressway traffic cooperates). You can easily see Philadelphia's skyline from City Avenue, beckoning like Oz. The avenue is home to two important universities, St. Joseph's and the Philadelphia College of Osteopathic Medicine, which add enormously to the action.

But so much of the recent development seems designed to put a hex on pedestrian life. That includes St. Joe's boorish and bulky dorm, which hovers oppressively over a three-foot sidewalk, and the equally bloated Mansions at Bala, which turns its ugly backside to the avenue. It seems almost Third World the way that waiting bus commuters are forced to huddle against the buildings to protect themselves from oncoming traffic.

Planners on both sides of the road believe it wouldn't take much to make things better. The new zoning would widen sidewalks to eight feet and would include a green buffer and, ideally, bike lanes. They'd like to see the surface lots infilled with apartments with ground-floor shops and eateries. Garages would replace the wasteful lots.

Some gas stations and car-repair places would go, too. That might free up a few key corners for modern office towers that would help City Avenue compete with its corporate nemeses in Conshohocken, King of Prussia, and Radnor. While City Avenue struggles with a 20 percent vacancy rate, those competing office nodes lure taxpaying tenants with up-to-date space, high-speed wiring, and the latest amenities. City Avenue should be outshining all three, given its convenience to the airport, 30th Street Station, and downtown Philadelphia.

Sensible as the planners' ideas sound, Lower Merion's residents remain suspicious. The zoning proposal, which has been kicking around since 2007, was tabled yet again this month. Township commissioners intend to hold workshops this summer to discuss the changes, in the hope of holding a final vote on the plan this fall.

The sticking point, as one might expect, is the prospect of tall towers sprouting on the suburban side of City Avenue. Although there are several multistory offices there now, including the 120-foot-tall GSB Building near Belmont Avenue, the new zoning would allow towers to rise to 200 feet. On the Philadelphia side, they can be as tall as 350.

The proposed changes follow height increases in Lower Merion's other commercial areas. As local civic leader Teri R. Simon points out, the township should have completed a comprehensive vision plan first, before undertaking piecemeal zoning changes. Other neighbors also worry, not unreasonably, that the combined development could further overload the stressed roads that lead to City Avenue.

Point taken. But the benefits of the City Avenue zoning changes outweigh those concerns.

Sure, future towers might be taller, but the more important thing is that they will be friendlier. Right now, Lower Merion's short, squat, substandard offices rule over a kingdom of parking lots. Each sits on its own, huge landscaped block. People drive to work, drive to lunch, drive for errands, and drive home. No wonder the traffic is horrendous.

Under the new zoning, future towers would be taller and skinnier, and they would be sited much as they are on Philadelphia's Market Street - close to the sidewalk, with ground-floor retail. Allowing apartments would also provide the kind of housing option that Lower Merion's empty nesters and young couples now have trouble finding locally.

Certainly, some opposition to the zoning plan stems from a fear that it will urbanize leafy, suburban Lower Merion. But City Avenue is already a high-rise, commercial hub; the changes will make it a better one.

Contact architecture critic Inga Saffron at 215-854-2213,, or @ingasaffron on Twitter.