The unpleasant commuting experience that goes by the name of September Shock isn’t a sudden blow that arrives right after Labor Day. For many drivers and transit users, the summer slumber begins to lift in late August, as students begin to return to school, and continues into the early fall.

Nonetheless, many travelers in the D.C. area will notice some unwelcome thing — more trouble finding a space in a Metro garage, a little longer time getting through an intersection, a bus that’s impossible to board — that tells them they need to have their wits about them again, looking for little advantages and avoiding certain annoyances.

Here are some things — including good things — to be aware of during the fall commute.

Northwest Branch bridge

Drivers will encounter a new traffic pattern this month at the Capital Beltway bridge over the Northwest Branch in Silver Spring. Three lanes will go to the right of a work zone barrier, and the fourth will go to the left of it. To keep all lanes open during rush hours, the pattern has shifted periodically during the lengthy rehabilitation project.

With or without construction, this stretch near the Beltway’s interchange with Interstate 95 is one of the region’s traditional trouble spots, particularly on the outer loop. Last week, this area was one of the early warning signs of September Shock, as traffic steadily worsened during the morning rush.

HOT lanes construction

Construction workers will be busy on both the Beltway and I-95 in Virginia this fall. The high-occupancy-toll lanes on the Beltway probably will open before winter, and many stretches of pavement look done. But the most complicated parts of the project are the interchanges at I-66 and at the Dulles Toll Road, and there’s work to be done there.

All lanes are scheduled to remain open at rush hours, but drivers should watch for slow-moving construction equipment on the left sides of the inner and outer loops.

The I-95 HOT lanes project just got underway this summer and isn’t scheduled to be done until 2014, but drivers will notice the impact this fall. They may include slower travel times in the high-occupancy-vehicle lanes. Full closings of the HOV lanes may occur from 8 p.m. to 4 a.m. every night, and one lane may be closed until 5 a.m.

Rush Plus

Metro began its rush-hour service realignment on the Blue, Orange and Yellow lines in late June, so September will be the first full month for Rush Plus outside of vacation season.

Blue Line riders have complained all summer that the new rush-hour schedule has resulted in more crowded trains. But don’t look for any major adjustment in the service. Metro officials say the Rosslyn tunnel is at capacity. And they’re still figuring out how they will add in the Silver Line trains.

Sporting events

After this weekend, the Washington Nationals have just two more regular season homestands at Nationals Park. But for the first time, we may be discussing transportation to post-season games in October. Depending on the team’s fortunes, some of those games could be on Friday and Saturday nights, when Metro operates till 3 a.m. On Sunday through Thursday nights, Metro closes at midnight. If Metro stays open after that, some entity besides Metro will have to agree to pay for the overtime.

The Redskins will start generating traffic Sunday, Sept. 23, when they play their first home game at FedEx Field in Landover. The D.C. region’s college football teams will be back in action on Saturday afternoons. So watch the schedules for these seasonal traffic magnets.

New SmarTrip rules

Starting this month, Metrorail riders need to have at least $1.20 on their regular SmarTrip cards to enter the stations. For riders using a reduced-fair senior/disabled SmartTrip card, the minimum is 35 cents.

The Metrorail Fast Pass, good for seven days of unlimited Metrorail travel, is now available for purchase only on SmarTrip. But the paper Fast Pass cards can be used through Dec. 31.

The rebate program for purchases of SmarTrip cards took effect this month. People who buy a new SmarTrip card for $5 can get a $3 rebate after they register the card online. The $3 will be credited to the card five days after its first use.

Unfortunately, not all stations have vending machines for SmarTrip card purchases. Although 47 stations have them, the distribution won’t be complete till November, the transit authority said.

Metro track work

The fall will be a busy season for Metro’s weekend track work program, in which trains share a track around work zones or are replaced by free shuttle buses along a closed portion of a line. The program will take a break at Thanksgiving and around the December holidays.

One of the most extensive disruptions is scheduled to occur over the Columbus Day weekend (Oct. 6-8). The transit authority plans to use buses instead of trains between Stadium-Armory and Largo Town Center and Minnesota Avenue on the Blue and Orange lines. On the Red Line, buses are to replace trains between Fort Totten and Silver Spring.

What’s better

We can end on an upbeat: Commuters may find this fall’s traffic a bit easier to deal with because of a string of improvements across the region.

I hope Maryland drivers heading to work in the District or Virginia this fall will discover the advantages of the new ramp from southbound D.C. 295 to the 11th Street bridge. This provides a convenient route to downtown Washington and to the 14th Street bridge over the Potomac. The outbound ramp, from the 11th Street bridge to northbound D.C. 295, is scheduled to open later this year.

In Virginia, the major breakthrough of the summer was the full opening of the THRU and LOCAL lanes on the Beltway’s outer loop approaching the Woodrow Wilson Bridge. That should make fall traffic a lot easier for both local and long-distance drivers.

This month, another big step was taken with the completion of the ramps that will make a direct connection between the eastbound Dulles Airport Access Highway and the Beltway. That eliminates the extreme lane changes across the Dulles Toll Road that airport travelers had to make to reach the Beltway.