He explains: “For the transgression of mar’it ha’ayin is definitely involved since, by and large, most [drivers] will not allow people to travel without payment and people will come to suspect that the individual paid the fare and also violated the prohibitions of carrying and handling muktzeh.”
He continues: “And even if all residents of the city will not be required to pay, Heaven forbid that we should permit such a public matter that is a weekday activity – uvdin d’chol – as most passengers travel [on these busses] mainly for business and work. Thus, [riding on them would create] a great chillul Hashem.”
He adds: “There is also somewhat of a proof to this prohibition from the Gemara in Beza (25b), where we find that R. Ammi prohibits people from carrying a person sitting in a sedan chair on their shoulders on Shabbat or the festivals. Rashi explains that he prohibited it because it appears like an uvdin d’chol….Therefore we might compare this case to busses and trains that travel far. For even concerning the Gemara’s case, the prohibition was not due to going beyond the techum. Rather, [it was] due to uvdin d’chol. Surely regarding [busses and trains], the same rule should apply.”
Rabbi Feinstein then concludes, “In general, one should not be lenient in such an unusual matter.”
What I find most intriguing about this responsum is that he does not advance many of my concerns, especially the possibility that the driver might be Jewish. This alone should render riding on a shuttle prohibited.
Indeed, American law guarantees access to any type of employment to any person, regardless of religion, race or creed. This is especially true for municipal jobs. And the employer of the Florida shuttle you mention in your question is probably your local municipality, especially given that it is subsidized and free. After all, it is highly unlikely that a private sector employer would offer free fares on his busses. Therefore, in light of the high rate of intermarriage today, even someone who seems to be not Jewish can very possibly be the son of an unaffiliated Jewish mother – especially in urban localities where there is usually a higher concentration of Jews. Thus, it is entirely possible that the municipal employee driving the shuttle is, in fact, a Jew.
Yet this concern is not expressed in Rabbi Feinstein’s responsum. Which brings us to the assumption that he – and, in our time, Rabbi Feinstein is the most recognized authoritative halachic source – would not sanction riding on a shuttle on Shabbat even if we could guarantee that all the concerns we mentioned did not exist.
In Rabbi Feinstein’s view, the appearance of Jews getting on and off busses is mar’it ha’ayin and a great chillul Shabbat. Thus, we conclude that there is no room to grant a heter to ride a shuttle on Shabbat.