LEWISTON — A crowd of people attending the 6th annual Build Maine conference Thursday rounded the corner onto Middle Street and waited to watch the next demonstration.

A small crew from Public Works, and Lewiston Police officer Joe Philippon — waiting by two dump trucks — quickly went over the plan and temporarily closed off the normally one-way road.

The two trucks, acting as if the road was now open to two-way traffic, then slowly drove past each other as conference-goers snapped photos and videos on their phones. The drivers had just a few feet of wiggle room to navigate the road.

The idea behind it? According to Build Maine organizer Kara Wilbur, turning the one-way road into two-way traffic creates 10-foot-wide travel lanes, making it narrow enough to force larger vehicles, in particular, to slow down.

She said earlier this week that there is resistance to 10-foot lanes in designing traffic patterns, but that they have been shown to slow down vehicles.

Build Maine is an annual urban planning conference that brings together professionals in planning, engineering, architecture and other fields, and the real-life demonstrations usually consist of traffic tests designed to slow down vehicles to make roads and intersections safer for pedestrians.

The two drivers did two passes at about 5 m.p.h. The first time, they had about a two-foot window as the onlookers clapped in approval. The second was a little closer, perhaps to add a layer of drama. When it was complete, Wilbur wanted to talk to the drivers about what they noticed.

They seemed to think it was pretty easy.

When she asked the drivers if they felt they could have passed each other going 20 m.p.h. faster, one driver was confident he could. But, he wouldn’t, he said laughing.

Jon Elie, highway operations manager for Lewiston Public Works, was among the crew on Middle Street on Thursday. Before the crowd arrived, he measured the roadway width from car to car. (There is on-street parking on both sides.) It was about 21 feet, he said.

After the demonstration, the Public Works staff said that while the 10-foot lanes were manageable right now, it would be a much different story in the winter. The same trucks are much wider with plow gear attached, and the roadway width is often reduced due to snowbanks.

As part of this year’s conference, the organizers also installed intersection tweaks at Main and Middle streets, where a “left turn traffic calming” test was built using plastic bollards and temporary curb material placed inside the crosswalks.

On Bates Street, an “advisory lane” was created between Main Street and the Royal Oak Room, which is hosting the two-day conference. An advisory lane roadway has a dedicated center lane for two-way traffic, with no marked centerline, and is designed to reorder the space in the street to slow traffic and make it safer for people walking and biking.

Last year, the conference put a focus on tangible city projects like public art, including a mural by renowned street artist Arlin Graff on the Centreville parking garage.

In 2017, the organizers installed an ambitious traffic pattern on Lincoln Street, with protected bicycle lanes.