But it's not just about road repair. Fossil fuel use externalities are not currently reflected in the price of gas.
Ideally, we should keep the gas tax (even increase it) to cover the damage done by gasoline and institute a road-use tax. We certainly should not replace the gas-tax with a road tax.
Further, I think it's more than reasonable to keep the cost of road maintenance in gasoline-tax. This further incentivizes people to use hybrids/electrics, a technology which in its early stages of development would benefit from an uneven playing field.