Residents of the District, commuters from the Maryland suburbs and transportation planners want to solve the rush-hour congestion on 16th Street NW between Silver Spring and downtown.

Their ideas include more buses, better management of the existing service and dedicated bus lanes. But Ed Tennyson, a transportation engineer and former deputy transportation secretary of Pennsylvania, is an advocate for light rail.

He bases his case on the reliability and people-moving capacity of such systems in heavily used commuter corridors.

Dear Dr. Gridlock:

Phoenix commuters take the light rail in 2011. In 2009, the city opened a light rail line from Northwest to Mesa, 20 miles, and it expected 25,000 weekday riders. Now it has 46,000. (Laura Segall/FOR THE WASHINGTON POST)

When a bus is 20 minutes late on a three-minute headway, there will be seven busloads of people trying to board one bus. It cannot work well. More than likely, with a delay like that, a bunch of buses will come along. But riders, who cannot be sure of that, try to all jam on the first one, making it even later.

With gridlock, buses just cannot work well.

Metro puts three types of bus service on the 16th Street S Line. One, the S9, has limited stops, another service is local and a third is a short turnaround covering only the busiest segment of the route.

What 16th Street needs is light rail, with a double track in the center of it so that the streetcars will have nothing in front of them after they stop to load and unload. Left turns would have to be banned, or provided with a left-turn lane off the car tracks that would be controlled by a signal.

Light rail could attract 15,000 weekday passengers, with 1,500 one-way in the peak hour. Automobiles in that same lane can carry only 900 people per hour with traffic signals interrupting their movement. Increasing the capacity of the street will reduce the congestion and pollution. If you ever get to Phoenix, look and see how they did it.

In 2009, Phoenix opened a light rail line through the city from Northwest to Mesa, 20 miles, and it expected 25,000 weekday riders. Now it has 46,000.

Metrorail boosted transit use in our area by more than 300 percent from 1976 to 2013. Light rail cannot do that well, but the Transportation Research Board says it is likely to attract 35 to 43 percent more riders than buses on the same line. I do not recommend a subway for 16th Street NW, as it would cost far too much for too few riders when we already have the Green Line nearby.

But back in Phoenix, they are so pleased with their light rail line results that they are extending it on both ends.

Ed Tennyson, Vienna

DG: The people-moving ability of light rail is greatly enhanced when the transit vehicles have a travel path all to themselves. This would be different from some of the other transit projects the Washington area is getting familiar with.

A two-track light rail on a reserved path would take up a lot of street space. It would be different from the D.C. streetcar line that’s about to open on H Street and Benning Road NE. Those rails are embedded in regular travel lanes. And it would be a bit different from Maryland’s proposed Purple Line, which, on some streets, particularly Wayne Avenue in Silver Spring, would share lanes with other traffic.

Negotiating routes can take longer than laying down tracks. The District government spent many years working with communities on where it would begin operating its first streetcar line in half a century. Michael Madden, the Purple Line project manager, has spent several years in street-by-street conferences with residents over the best route for a 16-mile light rail.

The District does envision building a north-south streetcar line, but the nine-mile study corridor is east of 16th Street. At present, the D.C. government has no plans to build any light rail line of the type Tennyson envisions.

The District will have to come up with new ways of moving a lot more people through the city center. There’s no fighting that. But exactly how this is to be done will be the subject of many more fights.

Metrobus alerts

Bus riders subject to the daily whims of traffic congestion could do this to help themselves: Sign up for the electronic alerts that Metrobus sends out when the buses are delayed or detoured.

Metro launched the alert system for bus riders in February 2012. By the end of last year, 8,258 people had signed up to receive them by e-mail or text. Considering that there are 448,000 trips taken on Metrobus during a typical weekday, the number of people signed up to be notified about transit problems is tiny.

Signing up for the service doesn’t mean your account is going to get flooded with every single notice every time a Metrobus in the region has an issue. You can adjust the settings to cover the routes you use.

Don’t rely on any single source of information to plot your course during a service disruption, but do add the e-alerts. Metro’s sign-up page is