[mixmastamyk]

The smoothing doesn't increase the road capacity, though there is likely a small benefit to mitigating the negative effects of merging.

The big benefit, which the grandparent concedes, is the reduction of unnecessary fuel usage, wear and tear on the vehicle and driver.

So, I consider it a win regardless.

[wbeaty]

The papers I've seen on this conclude that rear-end accidents are the major issue. Smoothing the waves can eliminate immense rush-hour delays, if this eliminates panic-braking that can cause minor daily accidents. Or as they say, "speed differentials are dangerous." In I-70 Colorado they claim that police pace-cars used to smooth out the fluctuations have cut the accident rate in half.

In theory the waves can represent a bottleneck, since the close-packed regions are low-flow, but the wide empty regions are also low-flow. If the smoothed wave results in traffic flowing at 35-40MPH, then smoothing will increase the flow, since the peak flow rate takes place at 35-40 MPH. But the increase isn't enormous. I think they said ~15%. That's nothing, when compared to the effects of removing an accident scene from a rush-hour commute.

You can play with those online JAVA simulators: set up unstable conditions on the ring-road, watch the initial flow, then after traffic-waves develop, watch the flow again. If enormous waves appear, the flow drops by ~25%, but if a string of small waves appear, the decrease is less than 10%.