To be honest, I haven't been very familiar with the concept of tactical urbanism until just a few weeks ago. It was then when Jonathan Fertig, a local architect and activist, decided it was time to fix a few bike lanes in Boston and make them look the way they should have looked from day one. Clearly, just a strip of green paint was not enough to stop drivers from using those lanes and parking there. Fertig then created his own barrier between the bike lane and the car traffic by placing flower pots and cones, making these "protected" bike lanes a little bit safer. If you wonder whether this home made barrier worked, take a look at these pictures:
Apparently, adding $6 flower pots and a few cones is all you need to keep drivers at bay and make life easier for cyclists.
The pots stayed in place for quite a while until the city of Boston installed a proper barrier several days later, clearly motivated by Fertig's action and all the media buzz it created.
After reading this, I started looking for more examples of tactical urbanism. Just a few days ago we were celebrating PARK(ing) Day, an initiative to temporarily convert metered parking spaces into tiny parks or simply areas that people, not cars, can use and enjoy. There are many examples on internet like these:
PARK(ing) Day examples - turning some of those many curbside parking spaces into livable spots.
In general, tactical urbanism is a really neat idea. Changes are usually introduced within hours, not days, so they happen quickly, yet they are temporary so they don't interfere with the lifestyle of most city citizens long enough to become burdensome. At the same time, they stay in place for some time and many locals have a chance to get familiar with them and try on their own how their streets would look and feel like if they were more livable. That can convince the undecided that changes are necessary and the full length of the street doesn't necessarily has to be filled with parked cars.
Yehuda was into tactical urbanism before I even heard about it (Source: yehudamoon.com).