Why are vehicles with maximum laden weight of more than 3,500kg (Heavy Goods Vehicles) given a higher bonus compared to vehicles with maximum laden weight of less than or equal to 3,500kg (Light Good Vehicles)?

Heavy Goods Vehicles are more pollutive than Light Goods Vehicles on a per vehicle basis. Removing pollutive heavy vehicles from the roads will result in commensurately higher health benefits. Hence, higher bonuses are given to incentivise owners of Euro II/III heavy vehicles to switch to cleaner alternatives.

Soure: LTA