Photo by Tim Brown

As school bells ring, summer vacations end, and Congress gets back in session, District residents should brace themselves for what area traffic experts have dubbed the “September Shock.” This very predictable month of delays returns, with the addition of worsening traffic congestion created by Metro’s SafeTrack program.

To prepare D.C.-area commuters for what’s to come, the National Capital Region Transportation Planning Board recently published an analysis of September traffic patterns over the past six years.

The study found that the average increase in morning travel delay between August and September ranged from 15 percent in 2010 to as much as 45 percent last year. For drivers, this means that you could have spent at least an extra half hour or more sitting in September’s traffic than August. Over the course of a week, that’s several extra hours of pacing along at a dreadful five mph.

Photo via NCR Transportation Planning Board

The study also found that relief comes in the afternoon, making morning hours the real culprit for “the month-long phenomenon.” While traffic did increase most years during the afternoon hours, the percentages were much smaller than in mornings. And in 2010 and 2014, afternoon congestion in September slightly declined.

The TPB recommends that commuters adjust morning departure times, if possible. They also say that September might be a good time to start working from home (or you can post up at a neighborhood coffee shop or another spot with free Wifi).

The map below gives a breakdown of when and where the region’s September traffic is at its worst, in comparison to August.

via NCR Transportation Planning Board