Chart shows the monthly variations in morning travel time delays during recent years, with a focus on the change from August to September. (Transportation Planning Board)

Did you experience “Terrible Traffic Tuesday” during the morning commute? Judging by traffic maps and cameras, the peak period was slow on many stretches of highway, but by Washington’s traffic standards the overall result wasn’t terrible.

Traffic researchers may not be able to ease the pain of commuting, but at least they’re making it more understandable. In recent years, data analysis by the staff at the Transportation Planning Board has given us a much better idea of how travel time delays vary from month to month. And it’s also explained the collective experience drivers endure as summer vacation season ends at Labor Day.

Public school systems in Virginia launched their semesters on Tuesday, completing the regional cycle of school start-ups. If you were stuck behind a school bus, you noticed this, but there’s also a collective impact: School openings mean many parents have less flexibility in setting their travel schedules. That’s one of the factors that concentrates the peak of the peak traffic at rush hours. Drivers in the District and the Maryland suburbs got their latest experience with that at the end of August when schools reopened in those jurisdictions.

This Tuesday morning, traffic was slow in the usual slowdown areas, including the northern part of the Capital Beltway’s outer loop through Silver Spring, the inner loop approaching the Legion Bridge, inbound I-270, D.C. 295, I-395 approaching the 14th Street Bridge and on I-66. But I think many drivers would say they’ve seen worse, even on some days over the summer.

The traffic study released last week by the Transportation Planning Board showed that the Tuesday after Labor Day isn’t consistently terrible. It’s got the same reputation among drivers that Black Friday has among holiday shoppers, but neither date is necessarily the peak of woe for the congestion phenomenon their titles describe.

In most of the recent years studied, the planning board staff found no clearly terrible pattern on the Tuesday after Labor Day. The staff said the Tuesday traffic “blended in with the broader ramp-up of traffic that occurred between August and September,” which you can see in the chart at the top of this posting.

The exceptional year was 2015, when reality matched the legend. Last year, the Tuesday after Labor Day did display worse traffic than any day in August, the planning board staff said, “but there were worse days to come, both that week and the next.”

Traffic delays — overall — really do get worse in September, even if data analyzed by the planning board staff and other groups should make the effect less of a shock. From 2011 through 2015, the increase in travel delay from August into September ranged from 25 percent to 45 percent, according to the planning staff, with 2015 being the worst year.

The level of traffic data now available to both researchers and the general public is going to make personal traffic forecasting more like personal weather forecasting. You should be able to leave home with a decent idea of what conditions you will encounter.

At least, up to a point. Just as weather forecasters couldn’t account for what Hermine would do in your exact location, the researchers can’t tell you exactly what will happen on your commuting route. They can’t account for crashes or construction projects, for example, so there’s still an element of chance on every drive. With each new set of statistics, the researchers point out that their conclusions amount to an overview and that your results may vary.

Some things to be aware of:

  • The end of summer vacation season doesn’t mean an end to road work. The construction season in its various forms continues through the year’s end, though most projects will not involve work during rush hours.
  • The National Park Service is about to begin a construction project on Beach Drive, a narrow but important north-south commuter route through the District. My colleague Luz Lazo is monitoring that.
  • Metro’s SafeTrack maintenance projects will continue to affect traffic patterns in the corridors where the track work occurs. A new SafeTrack project will require continuous single-tracking on the Orange Line between Vienna and West Falls Church, which could put more stress on a portion of I-66. That one starts Sept. 15 and continues for 42 days.
  • The Virginia Department of Transportation has begun to set up the HOT lanes electronic tolling system on I-66 inside the Beltway. This should not be a big source of travel delays. It’s mostly off-peak work to set up gantries for when the HOT lanes open next summer.
  • Drivers and bus riders must deal with a disruption in their travels through Takoma Park, where the Maryland State Highway Administration has blockaded the Carroll Avenue bridge over Sligo Creek for a $12 million rehabilitation project. There’s a temporary bridge for pedestrians beside the roadway bridge, but a detour for vehicles is scheduled to remain in place until mid-2017.

Travel tip: I’ve noticed that some people who used the Twitter hashtag #TerribleTrafficTuesday this morning were reporting how they avoided problems. Yes, some did report local difficulties that included the impact of school openings, but others talked about either leaving a little earlier than they did during the summer or — even better — working from home.