Rethinking Tax Money for Road Maintenance

Apparently, the Department of Transportation (DOT) is claiming that because fewer people are on the road, less money is in the kitty to pay for road and bridge upkeep. Here's why: Each gallon of gasoline you buy is taxed at about 8%. This tax pays for transportation maintenance. Since higher gas prices have lead more people to take public transportation, walk, bike ride, or buy more fuel-efficient cars or hybrids, less money overall is in the kitty. However, even though you may think that fewer cars on the road would lead to less need for maintenance, you're forgetting that extreme weather conditions (along with heavy semi-trucks used for shipping) are to blame for much of the wear and tear. Bearing this in mind, should we raise the gas tax (which would potentially hit poorer people harder, who can't afford to pay $30,000 for a new hybrid)? Or start taxing based on miles driven, similar to California's new proposed pay-as-you-go car insurance? Or charge higher fees for vehicle registration? Or convert more highways into toll roads?