The incentive amount will not be dependent on the income of the individual or family. It's going to be dependent on the number of individuals and the composition of the family. It's going to be a fixed amount for the first adult, then a lower amount—typically half of it—to the spouse, and then a smaller amount again for each child, regardless of the income.
The effect of that approach, however, is that it is still progressive in nature. If you give the same amount to low-income families, who would typically spend less and pay lower fuel charges than a higher-income family would, they will end up receiving more than what the fuel charge will cost them. This is not the case for the higher-income family. In that sense, it's progressive in nature. The overall amount is distributed, but when you look at different classes of individuals, distribution can be different.