A streetcar comes to a halt on the test track along the west side of South Capitol Street in Anacostia. (Robert Thomson/The Washington Post)

If you happen to be aboard a D.C. streetcar when the operator hits the emergency brakes, it will feel like a Metro train lurching up to the platform — only more so. Hold onto a passenger railing with both hands for the several seconds it takes to bring the streetcar to an emergency halt.

By contrast, the normal braking is quite smooth. May all your braking be normal.

The District Department of Transportation is testing its first three streetcars along a track that runs parallel to South Capitol Street in Anacostia. After going through these basic checks, which I got to experience Monday during the brake testing, they will be transferred to their route along H Street/Benning Road NE for a lengthy period of practice runs.

A transit revival that now exists as lines on a planning map will then become a street-level reality for drivers, bikers, pedestrians and — around the end of the year — streetcar riders as well.

This first showing of the modern generation of streetcars should be watched closely by District residents and communities across the region where streetcars or light rail will share street space with other traffic and pedestrians.

Dear Dr. Gridlock:

I am writing about the opening of streetcar service on H Street in less than six months.

Like many supporters for alternatives to driving who like streetcars, I’d like to get one issue resolved. Historically, cities supported streetcar removal because they blocked traffic.

When the new operation comes, what will be different about it?

What is DDOT doing to avoid a repetition of the same complaints? To have track beds raised, to mark the lanes as streetcars only, to set traffic lights to give priority to moving streetcars — these are some ways used elsewhere. Another means is to forbid auto traffic from the streetcar lanes.

Or will history repeat itself, with the streetcar too slow to be popular?

— Leonard Adler, Rockville

The chance to experience streetcar braking on the test track, isolated from other traffic, reminded me of some essential characteristics of the transit system already familiar to Adler.

The streetcar operator can’t turn — only start, stop, ring the bell and toot the horn. So you’d best stay out of the way.

Traveling at 15 mph, with the test crew warning visitors to brace themselves, the emergency braking was a bit of a thrill. The operator hits a button, engaging an electromagnetic current that drops sets of large brake pads onto the rails, and the intense friction forces a dramatic halt.

If an operator had to do this in regular service, with many standees focused more on the swell time they’re having in the Atlas District than on the lane ahead, the experience would be anything but pleasant.

But the real sufferers might be those who failed to pay attention to the streetcar’s approach or who were driving too closely behind it.

The streetcars are bright red, like the D.C. Circulator buses, and should be highly visible. However, they are pretty quiet in normal operations. Don’t count on the roar of an engine to announce their approach.

The tracks along H Street/Benning Road are embedded in white concrete, so there’s no mistaking the route of the streetcars, but this is a regular travel lane and open to all traffic.

I’m not as concerned about the streetcars blocking traffic as I am about traffic blocking the streetcars. In normal service, five streetcars will be operating along the two-mile route. That shouldn’t have any more impact on normal traffic than the Metrobuses.

But the safety campaign that accompanies the arrival of the streetcars needs to be a strong one, and enforcement of traffic rules by DDOT and police needs to be vigorous.

Dr. Gridlock also appears Thursday in Local Living. Comments and questions are welcome and may be used in a column, along with the writer’s name and home community. Write Dr. Gridlock at The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or e-mail drgridlock@washpost.com.