Pope Francis leaves Catholic Charities in the District after blessing charity workers and the needy. (Brendan Smialowski/Agence France-Presse Pool)

The two days Pope Francis spent in the capital did as much as our annual Car Free Day on Tuesday to show commuters how nice travel would be if more people left their cars behind.

Car Free Day, hosted locally by the Commuter Connections service, is a personal journey in which you pledge to give up solo driving for a day and travel by transit, bike, carpool, vanpool or foot.

It’s a great way to support the environment and commuter sanity. But this individualized learning couldn’t match the papal visit’s collective impact in demonstrating the effect of keeping cars in driveways.

“The traffic here is the lowest I have ever seen!” proclaimed Alan Pisarski, a guy who knows traffic. Pisarski, author of the transportation study called Commuting in America, understands it as a concept. As a resident of the Washington region, he also knows traffic as an experience.

“Nothing on the Legion Bridge,” he said Wednesday. “Zero cars on the 14th Street Bridge. We need more religious events as a traffic calming tool.”

I lost count of the Twitter messages in which commuters begged the pope to hang around. That little black Fiat of his had us spooked about traffic congestion along the papal routes. So thousands of vehicles stayed in driveways when they might have been filling Metro garages, Potomac River bridges and D.C. streets.

Such a blessing.

I was worried about traffic and transit congestion as Francis moved from crowd-drawing event to event, through cordons of closed streets.

Typically, even one such gathering during a rush hour — say, the National Christmas Tree lighting each December at the Ellipse — is enough to send gooey ripples of congestion for blocks.

Wednesday’s popemobile parade around the Ellipse drew thousands of spectators to that high-impact traffic zone during what would have been the morning rush.

A wonderful thing happened: no ripples. It was like tossing a bar of soap into a bathtub and seeing it land with a thud because there’s no water to make waves. On the blocks around the Ellipse, a zone that encompasses some of the District’s busiest commuter routes, there was no effect because there were no cars to clog the streets.

Thousands of federal and private employees worked from home or took the day off. Those who did travel saw the effect and begged for a repeat.

While this was a collective learning experience, a repeat is unlikely. Pisarski suggested some reasons we can’t be that lucky all the time.

The main thing is that all those workers aren’t going to suddenly convert to full-time telecommuting.

Pisarski’s guess was that we would need one-third of the federal workforce to stay home for commuters to see a similar benefit.

Okay, but couldn’t they travel to their offices via transit?

“There isn’t enough capacity on Metro to handle that volume,” Pisarski said.

The crowds for the papal events were relatively small compared with Inauguration Day or July 4. But if their numbers had been added to more typical commuter runs on Metrorail, the system might well have been overwhelmed.

On a typical day, the transit authority is not able to get as many Silver, Orange and Blue line trains through the Rosslyn tunnel as Metro planners had hoped when the Silver Line opened.

For many riders, the typical result is a sluggish train trip. This would have been the case even without the special little disaster that befell the system Monday when a fire at a power substation near the Stadium-Armory station forced a temporary suspension of service.

When riders complained the next day about continued slow travels on the three lines, Metro officials finally shared the news that slowdowns stemming from the power problem could continue for several weeks.

For Metro, communication is a problem that rivals capacity. We would have had much more to talk about today if extra-large crowds of commuters and spectators had brought the issues of poor communication and capacity to the fore Wednesday and Thursday.

But Pisarski made another point. Commuting to and from the District doesn’t account for all our travel woes.

His afternoon travels included a trip up Interstate 270 and back down across the Legion Bridge about 4 p.m. “Standard congestion,” he said.

People go to many places for many reasons. Maybe people weren’t driving to work during the pope’s visit, but there was still “lots of shopping and other stuff,” Pisarski said. The traffic decline showed up on the spokes leading into the D.C. hub, but it was less noticeable elsewhere.

My conclusion: We need more than a break in the routine. We need to change the routine.

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@