Incorrect fuelling could be eliminated by changing the cross section design of the pump nozzle and fuel tank filler pipe. For petrol the nozzle and filler pipe could continue to be round, for diesel the filler pump nozzle and filler pipe should be square section. With the correct dimensions it's possible to ensure that only the petrol pump nozzle would fit the petrol filler and only the diesel nozzle would fit the diesel filler.