The two most popular at this time are both made by TML Studios and the vehicles used and controls are identical. Vehicles can be modified and many 'Mods' are available for both games, additional vehicles purchased in one game automatically work in the other. The simulators involve driving a bus through the roads, and depending on the mode stopping to collect passengers along a variety of routes, checking their tickets before they board the bus. Delays, accidents and breakdowns happen, throwing out the set time schedules, and as the game play progresses additional vehicles and garages can be purchased, drivers, maintenance staff and escorts employed. Regular refuelling and bus maintenance are required, fines are issued for speeding or causing accidents and money deducted for passengers missed or cancellation of routes.