ANDERSON COUNTY, Tenn. — Road crews will be doing bridge repairs along a stretch of Interstate 75 between Norris and Rocky Top for the next few weeks. The interstate will be down to one lane in both directions through at least May 23.
For most of Monday, traffic was backed up for a few miles in both directions around the construction site at mile marker 126.
TDOT is asking people to learn how to zipper merge to keep traffic moving smoothly through the construction zone.
The zipper merge is difficult in practice because it requires everyone to work together, leave some space between the vehicle in front of them, and take turns to act like "teeth on a zipper" at the merge point -- and it's a tall order to get thousands of drivers on the same page.
Here's the key: Everyone needs to leave enough space between them and the vehicle in front of them so people can merge smoothly without stopping or slowing down too much.
The zipper merge is also known as the "late merge" because vehicles in the lane that ends should wait to merge right as they reach the construction zone. Vehicles in the other lane should take turns letting merging vehicles in without slowing down or stopping, which requires both sides to be mindful of their speed and keep enough open space in front of them.
The tricky part is that a lot of people think they need to merge early when they see the arrow sign, but that creates one dense line of traffic and leads to longer backups when traffic is heavy.
Vehicles in the thru lane that moves through construction also need to avoid the urge to cut off merging drivers they think are "cutting in line." Likewise, vehicles in the other lane need to avoid the urge to merge early and shouldn't try to force their way into the thru lane.
Both lanes need to drive with the goal of cooperating, or else it will create traffic jams like the one on Monday.