“Terrible Tuesday” wasn’t so terrible, but Wednesday was wicked, and commutes are likely to worsen for many travelers as we move into late summer and fall. ¶ The phrases we come up with to describe post-Labor Day travel in the D.C. area put catchy labels on what’s actually a complicated experience. The broadest term applied by those of us who follow local traffic and transit patterns is “September Shock.” It’s better than using a one-day time frame, but “shock” doesn’t quite capture what builds up over several weeks as fall arrives.

Drivers notice that it takes longer to get past traffic signals. Highway trouble spots are more troublesome. Metrorail commuters have to park on a higher level in the garage, and bus riders find the schedules less reliable and seats more difficult to come by.

They contrast this with a happier time that actually was quite short-lived. For many, it’s late July through August, the time when school is out, vacations are in and Congress has left the building. All that goodness doesn’t evaporate in a single day, but it does disappear through September and into late fall.

The real difference-maker between deep summer and September is that so many people will now be trying to make the same trips at about the same time. A study by the D.C. region’s Transportation Planning Board showed the significance of trip times in highway congestion.

The decline in total driving that occurs in July and August is slight, the study said. Yes, many people take summer vacations, but those still around get out more because of the warm weather and extended daylight. The extra summer travel tends to be at midday or in the evening, rather than at rush hour.

When schools are out, parents have more flexibility in timing their work trips. If they don’t have to pack the children off to school and pick them up at set times, they can avoid the peak of the commute. That can lessen overall commuting delays, the study said.

That break ends in September. The study found that the average daily delay per traveler rose nearly 27 percent from August 2011 to September 2011. The average delay was 20.4 minutes that August and 25.8 minutes that September.

Meanwhile, total driving rose by only a moderate amount. Vehicle miles traveled went from 32.71 million miles in August 2011 to 33 million miles September 2011.

Metrorail ridership, which drops in August, will rebound this month, though historically, the average weekday ridership in September doesn’t match the totals for July, a month that tends to be an above average for rail riding, thanks to out-of-town visitors and plenty of activities. Metrobus ridership also rebounds in September from August lows.

10 travel tips for fall

Even as the overall commuting experience worsens, individual trips vary greatly, depending on the route. Here are some of the particular situations that will affect travel, for better or worse.

Beltway in Silver Spring. The rehabilitation of the University Boulevard bridge over the Capital Beltway has been underway for several months, but the orange cones and lane shifts are very evident on those two major commuter routes. The project is scheduled to continue into 2015.

Wisconsin Avenue. The Maryland State Highway Administration recently began a resurfacing project along the half-mile of Wisconsin Avenue between Bradley Boulevard and Montgomery Avenue in Bethesda. Work is scheduled to be done in fall 2014.

George Washington Memorial Parkway. Watch for a flashing beacon at the Mount Vernon Trail crosswalk over the parkway’s northbound lanes just before the Arlington Memorial Bridge. This warning system will be in place till early October. The test is part of the National Park Service’s much-needed program of safety improvements in the area.

New Metro garage. There’s a new traffic pattern at the Dunn Loring Metro station. A 1,400-space parking garage has replaced the surface lot, which will be the site of a second phase of the garage to be completed in late 2014.

D.C. streetcar line. The streetcar line construction recently shut 26th Street NE from Benning Road to just south of the now-closed Spingarn High School for about two months. The contractor will install two streetcar track switches in the westbound lanes of Benning Road. D.C. officials hope to open the H Street/Benning Road line late this year.

Route 29 in Gainesville. The major transportation improvement of the summer: The Virginia Department of Transportation shifted Route 29 traffic onto the new bridge that separates drivers from the railroad crossing on this busy commuter route.

95 Express Lanes. Construction of the high-occupancy toll lanes will continue to be the main roadwork event for the D.C. region into the fall. Although the lanes aren’t scheduled to open until early 2015, this year marks the period of maximum impact on travelers.

Virginia HOV hours. The HOV lanes on northbound ­I-395/95 now close at 10 a.m. rather than 11 a.m. weekdays, and the southbound HOV lanes open at noon rather than
1 p.m. The change will remain in effect until mid-October to ease southbound congestion during construction of the 95 Express Lanes.

Metro weekend work. Major track work in which buses replace trains through work zones will continue through fall, including the Columbus Day and Veterans Day weekends. (The Columbus Day weekend disruption on the Orange Line will not affect train service on the Monday holiday, Oct. 14.)

Silver Line. Work continues all along the route of the Silver Line, which will have four stations in Tysons and one, the first-phase terminal, at the junction of the Dulles Toll Road and Wiehle Avenue near Reston. Project officials had hoped the new line could open by the end of this year, but delays have pushed the opening to early 2014.