Patterns can certainly happen by chance. More often than not, however, there is an explanation for a repeating event sequence. A double dose of seat time in the WSB Skycopter, while subbing for the vacationing Smilin’ Mark McKay, made me keenly aware of a traffic pattern that no one wanted to see.

The WSB Traffic Team and I covered multiple bad rush hour crashes in a spot where traffic backups often begin. This is a risky friction point where cannonball-fast comes hurtling into helplessly slow.

Last week we covered no less than four marquee wrecks - ones that lasted a long time and/or were particularly vicious - on I-285 in both directions near the triple-decker Chamblee Dunwoody/North Peachtree/North Shallowford interchange (Exit 30) in DeKalb County.

Tuesday, September 13th, PM drive, I-285/eastbound (Inner Loop)

As the 4 p.m. grind to line up and ramp from I-285/eastbound to I-85/northbound (Exit 33) got worse, delays began on I-285/eastbound right before Peachtree Industrial (Exit 31). Someone lost control and flipped their vehicle in the left lanes, jamming traffic back into Sandy Springs and really doing a number on GA-400.

Wednesday, September 14th, AM drive, I-285/westbound (Outer Loop)

Traffic, as it almost always does on weekday mornings, backed up off of the busy Peachtree Dunwoody (Exit 28) and Ashford Dunwoody (Exit 29) roads. The right lanes of I-285/westbound slowed back into Doraville. Multiple cars - at least four - scraped together in the left lanes right before Chamblee Dunwoody/North Peachtree. DeKalb FD found them and blocked three left lanes. This crushed the commutes on I-85/southbound and Peachtree Industrial/southbound from Gwinnett County.

Wednesday, September 14th, PM drive, I-285/eastbound

At 6 p.m., traffic speeds pick up in Dunwoody, which then increases the risk of violent crashes. I-285/eastbound was starting to move better, but the ramps to Peachtree Industrial were really jamming up the far right lane of I-285. An SUV somehow turned over and landed back on its wheels, even with the Chamblee Dunwoody Road exit ramp. First responders initially blocked the left lanes, but then shut the whole freeway down to treat a patient on the right shoulder. WSB Triple Team Traffic issued a RED ALERT, sending push alerts on the WSB Radio App and our Triple Team Traffic Alerts App, to notify motorists of this major closure. Fortunately, all but the right lane reopened by 7 p.m.

Thursday, September 15th, AM drive, I-285/westbound

Much like the morning before, a few vehicles got in a rear-ender. They did, however, pull to the right shoulder, causing only medium delays. When DeKalb FD showed up and blocked the right lane, the delays again caused implications for drivers coming south from Norcross. This crash was minor, compared to the other three, but it lasted nearly as long.

All of these crashes spawned in the estuary of high and low speeds. That is no coincidence. As driving has become more reckless in the last couple of years, these problems have gotten worse. As motorists become more distracted, the mixture with high speed winnows reaction time when they encounter the tail end of a backup. The change in speeds creates a collision so percussive as to sheer off wheels, crush roofs, and launch automotive shrapnel.

Not once in this piece have I even mentioned the damage to flesh, bone, and soul that wrecks of this magnitude almost always cause. We covered that topic deeply one week ago and it should never be forgotten.

In my 18 years of covering Atlanta traffic, the crash count is not its highest when the most people are on the roads. As bad as, say, pre-holiday weekend Friday afternoon traffic is, cars are generally crawling together on the arteries. Nasty crashes really start when the traffic starts moving faster again and speedsters happen upon sluggish conga lines.

In looking at I-285 in Dunwoody, other factors like the unfamiliarity drivers have with new ramps or the narrow and shifting lanes in the work zone increase the likelihood for mishaps. But those externalities are mitigated when drivers decrease their speeds.

Some more caution by at least one driver would likely have averted the I-285 calamity in that stretch three weeks ago. That the massive I-285 big rig crash and fire happened at Ashford Dunwoody in the 2 p.m. hour on a Monday is no coincidence. That was also at the tail end of a backup into Sandy Springs, where fast met slow and carnage ensued.

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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