Many travelers thought the light traffic and uncongested transit during the visit by Pope Francis in September was a minor miracle. Now, the staff of the region’s Transportation Planning Board has measured it.

A report prepared by staffer Wenjing Pu finds that “overall, a modest reduction in traffic volumes led to a significant reduction in congestion and an even larger improvement in travel time reliability on freeways, and transit ridership notably declined for the week” of the papal visit to the District, highlighted by many events on Sept. 23 and 24.

Did this experience reveal the way to the promised land for commuters? Unfortunately, no. But it does help us understand the relationship between traffic volume, congestion and unreliable travel times.

These are the highlights of the TPB study.

  • Traffic volume on highways for the week of the pope’s visit was only 1 percent down compared to the week preceding, but traffic congestion was relieved by 5 percent, and travel time reliability improved by 14 percent.
  • On Sept. 23-24, the days of the pope’s public events, highway volume declined 4 percent compared to the same time one week earlier. During those two days, highway congestion decreased 10 percent and trip time reliability improved more than 30 percent.
  • During peak hours on the two key days, a 2 percent reduction in volume generally led to a 27 percent decline in highway congestion.
  • Transit ridership declined 7 percent in the week of papal visit and an average of 17 percent during Sept. 23-24.

Notice in particular that a modest decline in the number of vehicles on the highways has a dramatic effect on congestion, particularly at rush hours. This also meant that the time it took to travel was much closer to the time it should take to travel — if only we weren’t forced into unpredictable slowing and stopping because of congestion.

The next chart shows the dramatic comparison between the morning rush on Sept. 23, during the pope’s visit, and the previous Wednesday morning.

The report reviews the factors that contributed to these great days for commuters.

The federal Office of Personnel Management asked federal agencies to allow employees to telework, adjust their work hours or take time off. Many other employers also allowed telework and flexible work hours policies.

“The significant reduction of freeway and regionwide congestion during peak hours could be an indication of the effectiveness of such polices,” the report said.

Other factors may have been involved. Sept. 23 was Yom Kippur, and schools were closed in some jurisdictions. Also, some local transit services reduced or rerouted their buses on the roadways that were most likely to be congested during the visit.

The TPB staff cautioned that such experiences are not easy to replicate. The pope’s visit was a highly publicized event during a compact time frame. The amount of teleworking and the flexibility in workers’ schedules “was a result of an extraordinary event,” the staff concluded.

But it sure was fun while it lasted.