Traffic intersections are the estuaries of the urban ecosystem, the place where pedestrians, bicyclists, cars, and trucks all converge. That's what makes them both lively meeting places and dangerously fraught conflict zones.

Even though we've been told since we were children always to cross at the corner, we've seen a spate of traffic fatalities at Philadelphia intersections, in spaces ordinarily deemed safe. Only last week, Emily Fredericks, a 24-year-old pastry chef, was hit by a turning trash truck while pedaling in the bike lane across the intersection of 11th and Spruce. Lidia Procaccino was struck down a year ago by a SEPTA bus as she wheeled her grandchild's stroller in the crosswalk at 23rd and Chestnut. Her death occurred just a few days after a drunk driver sped through a Market Street crosswalk and killed Anna Gonzalez and Catherine Cardoza.

It's hard to know whether another traffic configuration or better markings would have made a difference in these cases. But Philadelphia's Streets Department has been experimenting lately with subtle design changes that cue motorists to proceed with caution across intersections. Corner bump-outs, speed cushions, midblock crosswalks, and cobbled paving stones have been installed to help turn speedways back into walkable streets.

Now, the city is about to introduce the traffic engineering equivalent of a shout: the raised intersection. There will be two on South Broad Street, at Chestnut and Walnut; two others, at Sansom and Moravian, will be reconstructed to make them more handicap-accessible.  Although the new crossings don't look like much yet, the project is an acknowledgment that the street dubbed the "Avenue of the Arts" two decades ago has now morphed into the Avenue of the Apartments, and its new residential population is starting to get the treatment it deserves.

Sometimes called a speed table, the raised intersection is one of the latest innovations in street design. When the work is completed in the spring, the entire box — crosswalks, curbs, the interior asphalt — will be slightly above the level of the rest of the street. The grade change is small, just 1.5 percent, but Deputy Streets Commissioner Richard Montanez says the additional height should be just enough to force drivers to slow down.

The arrangement is intended to make intersections safer for pedestrians. To signal drivers to slow down, the crosswalks will be finished in a vibrant, high-visibility red asphalt scored to look like bricks. All the corner curbs are being removed, so pedestrians can flow easily from one side of the street to the other. Eliminating the need to step off the curb is particularly helpful for people with sight issues and disabilities.

I encountered a raised intersection over the summer in the center of Decatur, Ga., in front of the historic courthouse. Not only was the space elevated and curbless, it was framed with crosswalks featuring vivid, pop-art flowers. The center of the box was made of white concrete instead of black asphalt. The eye-catching design effectively turned the intersection into a plaza that could serve as a ready-made stage for community events.

Given the location of the three curbless intersections on the Avenue of the Arts, they could do double duty as temporary public space. Originally, the city expected to have them completed in time for Pope Francis' 2015 visit, but Montanez says the undertaking proved more challenging than the Streets Department anticipated. Before the new surface could be installed, the underground drainage system had to be entirely reconstructed. To pay for the work, the city and the Avenue of the Arts Inc. raised $3 million from a state program funded with fines from red-light camera infractions.

The Avenue of the Arts sees the project as part of a larger effort to give South Broad a more residential feel. When the Avenue of the Arts was established in 1993, it was envisioned as Philadelphia's Broadway, with a string of theaters served by parking garages for suburban patrons. Millions were invested in fancy light fixtures, planters, and cobblestone-paved crosswalks.

Though the branding concept succeeded in creating a theater cluster on the avenue, the street really came alive after the opening of several apartment buildings — Symphony House, 777, and Southstar Lofts. There are now eight residential and hotel projects in the works, including Pearl Properties' Cambria Hotel at Locust, the Post Bros. apartments in the Atlantic Building at Spruce, and Alterra's Lincoln Square at Washington Avenue and the recently completed Griffin at Chestnut Street. Maybe the biggest sign of change is the opening of a welcoming, all-day cafe behind the concrete walls of the Wilma Theater.

The Avenue of the Arts plans to replace all its theater-themed '90s infrastructure with new designs, says Paul S. Beideman, who runs the organization. This time, the streetlights will be shorter, to serve pedestrians, rather than cars. "They throw more light on the sidewalks," says developer Carl Dranoff, who  plans to build condo towers at Spruce and Pine.

Focusing on pedestrians and residents is a far better way to revive the avenue than the foolish and wasteful art project installed on North Broad in 2015. Those light masts, which look like highway lights, cost the city a hefty $14 million, yet the sidewalks remain an uneven mess.

Still, there is room for improvement on South Broad. The stretch lacks some important amenities, such as public green space and bike lanes. A design competition held in 2012 offered some useful suggestions, but none has been realized. Perhaps whoever buys the city's turquoise-colored health center on the corner of Lombard Street could replace its small surface parking lot with a park?

One reason it cost $1 million apiece to create the raised intersections, says Montanez, is that they are prototypes. Now that the city and its consultant, Urban Engineers, have gotten the kinks out the design, he believes the price can be reduced significantly, allowing the city to extend the traffic-calming measure south along the avenue.

Why limit the improvements to South Broad Street? The city is full of dangerous intersections, all waiting to be raised and made safer.

Streets Department workers removed granite blocks this fall from a crosswalk on South Broad Street. The pavers were part of the original, '90s design for the Avenue of the Arts.