Perhaps, but it is still problematic.
The most important one was mentioned earlier. It offers an implicit advantage to Americans. In the olden days we would call this American-centric. These days we would call it prejudiced. Claiming that it is prejudiced is valid since it is effectively asking different people different questions. To the American, it is asking them to identify taxis. To a non-American, it is asking them to solve a riddle.
To highlight that point: most of your criteria relied upon cultural factors. Those taxis have no resemblance to taxis in my part of the world. Taxis in my part of the world are private vehicles with a small magnetically mounted "taxi" sign on the roof. There is no consistency in colour, little consistency in type of vehicle, and they most certainly aren't covered with advertising. I also wouldn't be surprised if there are a handful of utility van used as taxis in my city, since taxi companies offer accessible services.
The game approach also implies some degree of understanding of captcha's. The approach you outlined assumed that the unidentifiable vehicle would not be treated as a valid answer and that more than one image would have to be selected, so you can look for patterns. Knowing the rules of the game may be fine if you are playing a game. It certainly isn't appropriate in the case of operating a business or offering a public service.