I want to propose a second more radical suggestion.<p>I think pacer cars might work very well for phantom traffic jams, but I very much disagree about &#x2F;how&#x2F; they should be used.  Instead of encouraging an over-capacity jam, I believe that the pacer cars should expressly communicate to other traffic something along the lines of.<p>&quot;Temporary&quot; &#x2F; &quot;Speed Limit&quot; &#x2F; &quot;Follow at XX&quot;<p>On a rear message board.<p>The pacer car would then draw out the stuck traffic in to the space &#x2F;ahead&#x2F; of the jam and encourage the compression wave to expand to the front instead.