We do a lot of traffic control in our area. We have a major single lane US highway, lots of blind curves and over 6 % grade. One of the first things we do on a scene is set up a safety zone. Sometimes that means stopping traffic but often all we have to do is slow traffic ahead of the accident so the guys around the curve at the scene can direct them around. We carry the requisite vests/wands/signage but often folks still just fly past us. Stopping traffic is easier because we can block the lane but that causes other safety issues especially on a single lane .
Folks tend to abide by "STOP" signage but ignore "SLOW".
This is a day and night issue, although night seems worse.
How do you slow traffic ?