A known traffic axiom has become prominent this fall, especially after the recent time change. The crash counts spike when traffic is light in one spot and then suddenly slow the next. Drivers in the speed limit-plus-zone peg their speedometers and then have very little time to react when their racecar (grocery wagon) encounters a line of brake lights. This has shown its teeth since the time change and and during unpredictable holiday traffic flows.

When the clocks fell back a couple of weeks ago, the last hour of PM drive began taking place at dusk or in the dark. Without fail, early sunsets cause delays to increase and not all the reasons why are obvious.

The most apparent delay-culprit is the angle of the sun, which gets lower in the west horizon at the height of PM drive. The sun usually sets as the roads begin to get better, but autumn and early winter see very difficult sight conditions when traffic volume and delays peak. Sunshine delays are a real thing, as we know.

But the post-sunset jam sessions are more flummoxing. Recent evening rush hours stay rowdy all the way through the 6 o’clock hour and later, when the tides beforehand receded around 6:30 p.m.

One reason for this is because traffic is at its peak ugliness when the least people are out of town. Mid-fall is when most schools are in session, the least amount of people are taking vacation days, and extra-curricular activities in all arenas are in full swing. Fall is the bridge between summer vacation and the winter holidays.

But why is the late-PM drive traffic swell endemic to the fall pattern and not also in the height of spring?

Early darkness from late October and through December simply makes brake lights show with more contrast. When tail lights are brighter, reactions are more reactive and harsh. Multiplying these slight overreactions in the dark over thousands of drivers equates to far bigger delays.

After 6:30 p.m., as more people exit the road system, the lines of delays lessen or perforate. And those gaps open the door for aggressive drivers to zoom in, over-react and over-correct in the night time, and then pile into the jams. As I dismount from the WSB Skycopter each evening, Mike Shields and Alex Williams happen on a sudden string of crashes late in the rush hour. A fair share of the wrecks on the WSB Jam Cam involve multiple cars jacked up and into the left median walls - right next to the fast lanes.

We’ve just come off of an extremely busy Thanksgiving travel holiday and this phenomenon holds true in getaway traffic patterns, both day and night. Drivers from out of town are unfamiliar with the lay of Metro Atlanta. All drivers are encountering traffic in directions against the normal rush hour grains. Mix in the line of commercial freight trucks and the table is set for trouble to erupt with the wrong catalyst. The mixture of changing speeds is just that.

When drivers that aren’t expecting ensuing delays take advantage of the presumed void and floor it, they leave themselves and those around them very little margin for error. That error usually results in spectacular wrecks and those crashes usually spur more behind them.

So as we continue in the fall traffic pattern and gear up for Christmas holiday, we all need to take a breath. Prepare for your commute or trip by plotting out the directions on your GPS app before just blindly following them. Download the WSB Triple Team Traffic Alerts App to check what lies ahead on your commute and to hear reports my team and I record, which play automatically when you drive in the path of trouble. Then tune in to 95.5 WSB for traffic updates 24/7.

After all of that preparation, the next steps are even more simple. Slow down and expect the unexpected. Keep your hands off the phone and your eyes on the road. All of these achievable steps build in more time and leeway for when traffic goes wrong. And, as Atlantans, we all know that conditions on the roads can change their tunes at any time.

Drive safely this holiday season, my friends.

Doug Turnbull, the PM drive Skycopter anchor for Triple Team Traffic on 95.5 WSB, is the Gridlock Guy. He also hosts a traffic podcast with Smilin’ Mark McKay on wsbradio.com. Contact him at Doug.Turnbull@cmg.com.

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