More theoretical posturing from someone who probably never actually drives in traffic. Maybe he can get together with Leon James of Hawaii. The situation at a cloverleaf on-off ramp is entirely different from that on the road in general, because volume typically changes at a cloverleaf on-off ramp, and there's an additional lane in play for a short space.
This isn't surprising at all. The cars are slowed by the congestion, and it takes time for them to get back up to speed, either because the cars are slugs or people won't put their right foot down..
Except that the lower-density region created by the cars which sped up creates a buffer zone which absorbs the wave.
Inhomogeneities are what prevent traffic from flowing at the rate of the slowest vehicle. If you study what happens when a road is near capacity with homogeneous flow and then you introduce a perturbation, of course inhomogeneity looks like a problem. But that's not the real world. In the real world there are slowpoke drivers, large trucks which can't accelerate up hills, people wandering across lane lines who you don't want to be near, etc. The additional inhomogeniety introduced by pbutting these people is a benefit, not a problem.
