Gridlock Guy: Sunshine underrated in its role in Atlanta traffic delays

How the sun rivals rain in tripping traffic and the perfect kind of weather for a smoother ride.

As the dreary throes of winter begin playing their last, whimpering minor chords, the sunshine of springtime is clearing its throat for a bold song. Atlanta weather has produced some popular episodes in recent weeks, with Old Man Winter still stepping in to direct some shows, driving the show’s ratings down to a shady, dark corner under some Spaghetti Junction flyover ramp. But fair dolcet weather bears with it some sour news: people hit the roads when doing outside feels nice.

WSB Triple Team Traffic and I see that green tree bear that fruit quite often, especially from late-morning into early-evening. Clear skies, bright sunshine, and moderate-to-warm temperatures increase traffic volume metro-wide. When those sunny rays are closer to the horizon, they can grind traffic to a halt.

Regardless of the solar angle, good weather simply breeds bad traffic. This is hard to comprehend, in one sense, because people’s fixed work and school plans don’t really change because of cloud cover or small temperature swings. But discretionary errands or excursions certainly seem to rise when the skies part and the mercury rises. And that phenomenon scurries traffic about in unpredictable patterns and flows, causing more delays - and more crashes.

The correlation between certain weather types and bad traffic is not as gruesome with exceptional weather as it is with rain, snow, and storms. But the average person would likely guess that good weather and traffic ride directly on a plane. But they do not. Any kind of extreme weather - including extremely good days - causes slower traffic in Atlanta.

The best weather conditions for good traffic are a cloudy day with dry pavement. Ideally, temperatures would be slightly cool enough that people would prefer to stay inside, instead of leaving the house. The remote work options now allow for more of these discretionary commuting decisions. So the post-COVID norm aids good weather’s role in bad traffic even more now.

No matter the season, golden sunshine throws banana peels into weekday rush hours. Freeways and streets pointed roughly to the east get blinded in mornings and treated just the same for the rides the opposite ways home in the evenings.

The most notorious interstate sunshine slow downs are I-20/eastbound from Douglasville (especially at the top of Six Flags hill) to Downtown Atlanta, I-285/eastbound (Inner Loop) from I-75 towards GA-400, and I-75/southbound between Marietta and Northwest Atlanta in the mornings. And that is inversely true on the other sides of those median walls in the early-evenings.

But some PM drive patterns buck this trend. I-20/westbound between Lithonia and I-285 in DeKalb is traditionally a non-rush hour direction, heading towards Downtown Atlanta in the evenings. But it sees a big traffic push in the second half of each weekday that is more pronounced when the sun blares in drivers’ eyes.

I-575/southbound between Highway 92 (Exit 7) and the shade at Bells Ferry (Exit 4) works similarly in afternoon drive. From the WSB Skycopter, I see that stretch usually slow to 25-35 mph right before the sun dips below the west horizon. There is just enough inbound traffic out of Woodstock to make a slow down there.

There is also the dreaded reverse-sunshine slowdown, which causes drivers to hit the brakes when it glares from the rear view mirror into a motorist’s eyes. That sounds ridiculous, but we often see delays on sparkling, clear days on Highway 78 (the Stone Mountain Freeway) thru Tucker, in the rush hour directions, with the bright sun behind the cars.

Daylight Saving Time, where time “springs forward”, begins at 2 a.m. on Sunday, March 14th. This means that the sun will rise earlier in AM drive and, for now, set a little bit later in PM drive. This will temporarily shift sunrise and sunset away from the high peaks of traffic volume in rush hours. But as the days get longer on each end, that relief will subside.

If AM drive patterns hold and traffic volume makes its sharp rise after 8 a.m., the sunny effect in the mornings will continue to remain lower than before the coronavirus changed things. PM drive is also peaking earlier, which means that sunset will soon happen well after the highest traffic volumes. So we can hang our shade-providing hats on that.

But all of these “new normal” assumptions could fly out of the open car window, if enough people get the COVID-19 vaccine and remote work and school options again become the exceptions, instead of the norms. However, those are largely unknown factors.

All of this fine weather talk does bear a call to action. Keep the sunglasses handy in the car at any day or time. Dial down those speed to close to the speed limit in bright, sunny spots similarly to how you should when rain falls. Less speed breeds more reaction time and keeping one’s eyes on the road opens the door to make an evasive move.

The same good, unselfish driving rules apply, rain or shine. Don’t discount the driving danger of bright sunshine, especially when driving around a certain curve at a certain time of day. The springtime chorus should play in a joyous major key and not with the minor chords of tragedy.

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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