Eli5: How do road workers and pavers work on interstates and highways when traffic is oncoming constantly? How do they place the barrels and cones down? Do they just run an hope not to get run over? How do they plan it?
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I’m not an expert but a major highway in my area has been undergoing re-paving for months and I’ve seen them do it. Early in the morning (like 4 AM or so) they set up one of those large blinking signs with the arrow to tell you to move to the other way. Typically a half mile beforehand they’ll have another sign that says “left lane closed” or whatever it may be. Then once traffic stops going into that line, they put a guy on a truck who has a stack of cones and lays them down every ten feet while the truck moves slowly. I think the key thing to note with your question is that traffic is not oncoming constantly. If you’ve ever been on a highway at 3 am you’ll usually see it’s a ghost town.
They do it in the middle of the night. They go out with one of those big trucks that has the flashing arrow on top to tell drivers to change lines. They slowly drive along while someone in the back of the truck places barrels and cones on the road. By the time morning rush hour hits, the closure is already in place and the workers have a safe work zone.
Highway work is thoroughly planned and scheduled in advance. Sometimes it is scheduled for nights and weekends when traffic flows are lower.
Durectional Signs and light boards and warnings are placed a large distance back to give motorists time to move over and merge into other lanes. Sometimes a mile or more away.
As to placing cones, sometimes [special trucks](https://youtu.be/Z7QaUunpqoA) with robot arms and conveyors are used to place the cones down, other time it is workers on a flatbed truck with a lift gate manually placing each cone/barrel/bollard down. Most crews have a crash vehicle between the workers and approaching traffic. That large heavy truck has arrow boards on it pointing traffic away from the closed lane and a large crash barrier so distracted drivers hit it instead of the worker placing the cones.
There is a system. Start from the shoulder (non travel lane) and move in the direction of traffic. Place the cones at an angle to push the cars into the next lane over. Drive the cone truck in the now closed lane and continue placing the cones thru the construction area. Picking up the cones is the process in reverse-start at the end of the zone and drive in reverse (opposite traffic) picking up the cones and reopening the lane. End on the shoulder or breakdown line.
A police car will start driving in an S pattern with its lights on to block and slow cars down about a few miles back. A truck will drive down the empty freeway and start laying down cones. Other signs and warning will also be placed.
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