The sidewalks of Broadway are filled with, in no particular order, scaffolding, dogs, garbage bags, business signs, LinkNYC kiosks, tourists looking at maps, tourists looking at the architecture, tourists holding their bags, store displays, wholesaler mannequins, people looking at restaurant menus, bike racks, and, of course, people walking.

Often, those people on the sidewalk, jammed in around the rest of New York City’s detritus, outnumber the cars on the street — as they do on a small stretch of Broadway between 24th and 25th streets, where pedestrian volume can be nearly 20 times higher than car volume during afternoon peak times.

That imbalance is one of the arguments for a novel idea being tried by the city Department of Transportation along that stretch starting in June: a “shared street” where cars, bikes and pedestrians will roam together — without differentiation or fully dedicated lanes.

It sounds like chaos, but it could work

Shared streets are officially new to New York, though they have been tried with some successes elsewhere in the world, dating to the 1970s in the Netherlands. Beyond the benefits of more space for walkers, there have been safety gains, too. On London’s Kensington High Street, removing barriers and differentiation between traffic and pedestrians preceded a 43 percent drop in traffic-related casualties.

Similar, albeit less radical, measures to slow down traffic have already been found to reduce crashes: bike lanes and pedestrian islands that decrease long crosswalks along Broadway, for example. The theory is that street sharing could contribute further.

Shared streets lead to “more interactions” between pedestrians and drivers, says Caroline Samponaro, deputy director of the advocacy group Transportation Alternatives, which supports the project.

There will be a single choke-point entrance to the street for cars, which will only be allowed to travel 5 mph — some of the signals that show drivers “this isn’t your environment. It’s a pedestrian environment that you get to be in,” says Samponaro. This reconfigures the traditional mindset and “forces the person who can cause the most harm — the driver — to go slow.”

There are other possibilities beyond this single shared street off Madison Square Park: Jon Orcutt of the nonprofit TransitCenter suggests some of the smaller colonial-era streets below Chambers Street in Manhattan could get the same treatment — they’re not built for cars anyway.

Samponaro points to residential neighborhood streets in the outer boroughs, for example, where there’s a high likelihood of children playing and you don’t want vehicles speeding.

Could shared streets expand?

“It’s politically near-impossible to really restrict cars throughout the city,” says Sarah Kaufman of NYU’s Rudin Center for Transportation. A DOT spokeswoman says the agency plans to examine the shared street’s “feasibility to gauge the possibility of expanding the concept to other locations in the future,” though she declined to point to specific sites.

Yet the project is one more in a string of major reimaginings of the city’s streetscape that began in the Michael Bloomberg administration and continued under Mayor Bill de Blasio.

On Broadway itself — which is set to close to traffic briefly on Saturday in honor of Earth Day — Times and Herald Squares have become pedestrian plazas. The 24th-25th street block is already cushioned by a small island with chairs and tables that draw locals and regular workers in addition to tourists, according to a DOT presentation to the local community board. This is all a 180-degree change from the traditional way of designing streets with huge, forbidding boulevards, humans banished to the edge, with a traffic light their main protection (a vision that still exists in many parts of New York).

The major change will be experienced by the drivers.

On a recent visit to the square, a number of professional drivers hired by New York families were parked between 24th and 25th streets waiting for their charges — they said the shared street would be just another adjustment behind the wheel.

“It’s working perfectly now,” said Paul DiIorio, 59, putting down the book he was reading in the driver’s seat and gesturing at the bikes going by in their lane, the trucks speeding down theirs.

But he said pedestrian safety was always a concern. A former NYPD detective, he said he often witnessed the way drivers dominated the road, speeding through lights or around corners, only slowing or perfectly following the rules when they passed a squad car or saw one in their rearview.

The idea behind a shared street is to get to the same (or better) good behavior, but through design.