Steven Levitt of Freakonomics has a great post in favour of further petroleum taxes. Interestingly, he argues that carbon taxation to prevent global warming is less important than reducing congestion and traffic accidents for social welfare. I suspect that he is not properly factoring in the globally felt negative externalities of global warming, but his conclusion is nonetheless correct that at least a tax of USD 1.00 on petroleum is dearly needed.
The most economically efficient solution to the issue of congestion, ie a proper Pigovian tax, would be a system like London's centre where only those vehicles which have paid a daily fee may enter. Their system relies on sophisticated network of cameras and plate recognition software to automatically bill and fine drivers.
Traffic accidents are doubtless a problem which should be seriously considered. I would expect that insurance and lawsuits already captures those externalities, but I do think a tax on vehicle size and weight per mile driven would help to counter the runaway arms race of personal safety that exists in vehicle addicted nations. I am mostly referring to the exorbitant demand for SUVs particularly for women. The individual driver, surrounded by an armada of SUVs piloted by cellphone distracted drivers, is not inclined to purchase a Volkswagon Golf. Thus the rational individual, in the interests of self preservation, chooses to join the backwards collective. This lesson I learned quite vividly on my first visit to Texas.
Nonetheless, a gasoline tax would as Levitt suggests have a beneficial effect on many things including congestion, traffic accidents, climate change and obeisity.