[dleibovic]

I agree with you that the traffic speed improvements being due to the bike lanes is poorly supported.

But still, this shows that there is room for intersection/street design improvements that do not slow down cars while making it safer for bikes.

[bjterry]

I didn't consider this thought until reading your comment, but this is a potential example of Bastiat's "Seen and Unseen."[1] By re-engineering the roads with bikers in mind, they have created slightly faster roads for cars apparently by accident. But all of engineering is about tradeoffs, so presumably there would have been some way to make traffic even better if they didn't have to consider the fate of bicyclists at all. The authors seem to be portraying this as if it's something of a free lunch (although obviously reengineering the road has some monetary cost), but it's not. If they had spent that same money on an engineering effort directed solely at automobile traffic, they could have done better by drivers (again, presumably).

Of course, if they had actually drawn a lot of people to use bikes instead of cars thus reducing traffic, then it could be argued that engineering for bicyclists advantages drivers directly, but that doesn't seem to have happened.

1: The Seen is the result of the engineering effort that they undertook. The Unseen is the result of an alternative engineering effort with different goals.