There's probably a huge cultural difference here, but the image there sure does not look like a 30km/h street to me --- more like a 30mph one. That said, I've seen pictures of other European streets, far narrower and meandering, where even 30km/h would seem too fast. It is also launching a campaign with the slogan: “We drive 30 for each other.” Not surprisingly, the socialism is blatantly obvious.
Seeing as the social democratic[0] PvdA is currently the largest political party in the Amsterdam city council[1], with the greens a close second, that's all in line with what the people of Amsterdam want.
This is Europe. Socialism isn't a scare word here. If anything, it's a rallying cry.