Delhi's GRAP Stage 4 restrictions have been revised, making the 'no PUC, no fuel' rule permanent for all vehicles year-round. Additionally, out-of-state registered non-BS6 vehicles will be permanently barred from entering Delhi when GRAP Stage 4 is enforced. Previously, BS4 petrol vehicles, regardless of registration, could operate freely. Now, only Delhi-registered BS4 petrol vehicles will be permitted within the city during Stage 4, while out-of-state BS4 petrol vehicles will be allowed in the NCR but not Delhi.