Government could buy emergency petroleum reserve as futures
Many are commenting on the gasoline shortages and price increases involved with hurricane evacuation and other emergencies. Some people can't get gas to get out of the city. Others full up giant tanks even when they don't need it. Stations raise prices as supply drops and demand increases, as per the normal rules of the market. Some suggest the stations be price-controlled to stop this, but that would only result in even more gas hoarding by the public.
The government could instead have a strategic emergency gasoline reserve. However, it need not keep this reserve in tanks, it could "keep" it in the storage tanks of all the private gas stations, by arranging a special emergency-based futures contract with the station owners, in advance. Not all stations need participate, as long as enough gas for evacuation can be reserved.
During the emergency, it would be calculated how much fuel will be needed per vehicle. Each station would provide that much fuel to each vehicle. The simplest way to do this is to devise some long-lasting mark that will last at least a few days to a week, and for each station to put it on a car after delivering the fuel. Perhaps something as simple as a sharpie mark or other semi-permanent mark on the gas cap. This is unfair in that people with multiple cars could get extra fuel, but other systems, like vouchers and databases have their own problems. Vouchers would be lost or sold on the black market, unfortunately.
Any fuel over and above the contracted amount could be sold at market prices to those who want more fuel and/or wish to hoard. Probably quite high market prices. Fuel tankers could also be arranged to resupply stations with emergency reserve needs. Note that the customers could still pay a normal price for the reserve gas, reducing the cost of the contract. They would also sign a voucher at the station, on which random audits could later be done to confirm compliance. Stations would contract to deliver based on the minimum reserve they keep in their own tanks. There could also be a true reserve in government owned tankers to cover the slop factor.