"They followed me on motorcycle" is correct. DL's "They followed me in motorcycle." is wrong. Reported.
No, it's not wrong. The word "in" means "by" in this sentence. (eg.) "Vado in bici" translates: "I go by bike".
Hmm. Gordon_Gregory has said the English in is wrong, not the Italian in. So if your opposition to his comment is, as his comment intented, about the English phrase, we would have "I go in bike". Which is as Gordon_Gregory said, wrong. For the Italian, I agree with you, in is fine.
Agree, but they followed me by motorcycle is marked wrong September 2019. I flagged it. Yes "by motorcycle" doesn't roll off the tongue as easily as "by bike" or "by foot", but that's a matter of frequency.
This ("They followed me on motorcycle.") is what I wanted to type, but I suspected it would be incorrect, so snuck an article in. Unfortunately I chose the wrong article to sneak in - the - and was marked wrong. :-(
We do not know how many they are ..... nor how many motorbikes are being used : so I put on their motorbikes, even though the Italian has one motorbike. Another of those odd sentences - and I do not consider this clutter!
Yes, I would like it confirmed that the Italian phrase "in motocicletta" even though using the singular "motocicletta" can mean people followed "by motorcycle" possibly on plural motorcycles.