For light lorries (maximum laden weight not exceeding 3,500 kg), the height of the canopy structure must not exceed 1.35 times the height of the lorry's cabin when measured from the road surface to ensure the stability of the vehicle.

For heavy lorries (maximum laden weight exceeding 3,500 kg), the height of the canopy structure must not exceed 3.2 metres when measured from the road surface (regardless of the height of the lorry's cabin). Certification from a Professional Engineer would be required if the height limit is exceeded