The majority of the best-selling cars in the US are now available with SAE level-one automated driving features such as adaptive cruise control. As the penetration rate of these vehicles grows on the roadways, it is now possible to consider controlling the bulk human-piloted traffic flow by carefully designing these driver-assist features. This talk will discuss modeling, simulation, and field demonstration advancements that are needed to control automated vehicles to stabilize traffic flow at scale. Prior work on a closed course established that automated vehicles can eliminate human-generated phantom traffic jams that seemingly occur without cause, reducing fuel consumption by up to 40%. The talk will highlight the research challenges and progress towards demonstrating traffic flow smoothing with a fleet of connected and automated vehicles on the I-24 Smart Corridor in Tennessee, as part of the CIRCLES Consortium.