Congestion is a huge pollutant. Our nation's highways are more congested than ever, and when cars are stuck in traffic they idle and pollute. Furthermore, congestion wastes drivers' time.
Carpool lanes are designed to provide an incentive to share rides and limit congestion. However, these lanes often add to total congestion and pollution by forcing four lanes' worth of traffic into three.
An excellent solution to the congestion problem would be to raise the price of gasoline. When gas reached $4.50 this summer, driving was down, people were taking less trips and driving/buying smaller cars. This is perhaps the best possible time to implement higher gasoline taxes: gas prices are at their lowest since 2002, we have an extremely popular incoming president, and many states face urgent budget crises. For the near future this solution remains politically untenable, even if we make it budget-neutral by rebating the tax to our poorest citizens, or using it to pay for mass transit.
Building more lanes on our highways would ease congestion, reduce pollution, save people time, and create new construction jobs. Roads are also the cheapest form of transportation to build, when you measure cost per passenger mile traveled, and thus will provide the most benefit for the stimulus dollar. Solar and wind energy are becoming cheaper, but are not cost-competitive yet, and will add to our total energy supply.
Cars are the dominant form of transportation in our society and will be for some time. Mass transit is well-meaning but limited to a small share of the population, outside of urban areas. Currently our nation's roads aren't wide enough for the amount of cars on the road.
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