If a country has a pattern of tourists being targeted by criminals on public transport, that information is mentioned in the Consular Information Sheets. Follow these general guidelines when traveling on public transportation overseas:
The same type of criminal activity found on trains can be found on public buses on popular tourist routes. For example, tourists have been drugged and robbed while sleeping on buses or in bus stations. In some countries whole bus loads of passengers have been held up and robbed by gangs of bandits.
(Adapted from the Department of State Publication 10942 Bureau of Consular Affairs.)