Autonomous Train Technology Market by Grade of Automation (GOA 1, GOA 2, GOA 3 and GOA 4), Train Type (Passenger Train and Freight Train), Technology (CBTC, ETRMS, ATC and PTC) and Component (Camera, Accelerometer, Odometer, Tachometer, Radio Set and Others): Global Opportunity Analysis and Industry Forecast, 2019-2026