Simplify the following text for a Grade 10 native English-speaking person.
Original: These armed officers began overt patrols on the MRT and LRT systems on 15 August 2005 , conducting random patrols in pairs in and around rail stations and within trains .
Simplified: These armed officers began patrols on the MRT and LRT systems on 15 August 2005 , conducting random patrols in pairs in and around rail stations and within trains .