INDIANAPOLIS -- What the heck just happened?
Thousands of motorists were slowed or stranded around central Indiana Friday night into Saturday morning after a wintry mix caused road conditions to deteriorate quickly.
Some drivers were forced to stay in the vehicles for 9 hours or more while emergency crews cleared crashes, or simply had to block roads until conditions improved for safe travel.
The forecast earlier this week called for winter weather conditions Friday night, including some icing, and despite the efforts of INDOT and other local road crews, more than 200 accidents, 30 injuries and one death were the result of freezing rain that swiftly descended upon major thoroughfares around Indianapolis and across the Midwest.
Despite how it appears, roads were pre-treated by Indy Snow Force and INDOT, but a unique combination of elements overrode their efforts.
INDOT sent 600 trucks state-wide to treat roads and the Indianapolis Department of Public Works (DPW) had sixteen crews pre-treating streets Friday afternoon and an additional 12 drivers overnight. They activated an additional 40 drivers as of 2:45 a.m. once the worst of it was evident.
But in such frigid temps combined with falling precipitation, pre-treating roads with salt only helps so much.
So here's what happened:
The bitterly cold temperatures that had Indy colder than Antarctica and Alaska earlier this week caused the ground temperatures to chill to below freezing temps.
As a warm front of weather with precipitation moved in Friday night, snow in the upper atmosphere turned to rain as it fell, dissolving the pre-treated salt, then re-freezing on contact with the chilled ground, causing conditions to become poor quickly.
When that unique set of events combine, until crews can deploy salt on top of that layer of ice for traction, the pre-treating efforts are minimally effective.
Because the freeze happened so quickly, road crews weren't able to treat the affected areas until it was already too late.
Low temperatures the past few days caused pavement to remain well below freezing when rain moved in, causing the rain to freeze on contact.
— INDOT (@INDOT) December 17, 2016
INDOT’s primary weapon was to deploy granular salt just before and during this type of storm as plow blades can only scrape solid ice.
— INDOT (@INDOT) December 17, 2016
Granular salt provides additional traction while the freezing rain dissolves the salt. #INDOTWinterOps
— INDOT (@INDOT) December 17, 2016
RELATED | Icy road conditions make roads impassable | Stranded motorists evacuated from I-465 overpass via a ladder | 1 killed in crash on icy I-65 | PHOTOS: Freezing rain causes hundreds of crashes, massive traffic jams | Multiple counties under Travel Advisories
Officials at the Department of Public Works said they will send out 80 drivers Saturday to keep streets clear through the overnight hours. In addition, crews will continue monitoring road and weather conditions around the clock to address changing conditions.
