Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) are being introduced with the roll-out of BS VI norms, which were not a part of BS IV.  

• Real Driving Emission (RDE) will be introduced in India for the first time with the implementation of Bharat Stage VI emission norms.  
• It will measure a vehicle’s emission in real-time conditions against laboratory conditions.  
• Onboard Diagnostics (OD) has been made mandatory for all vehicles which will give the vehicle owner or repair technician access to the status of the various vehicle sub-systems.  

Source: MOEFCC