Excise tax is historically known as "luxury tax" and is strictly based on quantity. This is the tax taken from anything luxurious, or anything not necessarily needed to survive just like whiskey/alcoholic beverages, car, gasoline and cigarettes.
The best reasons applicable to the excise tax on gasoline are the following:
> to make gasoline prices more competitive - Other fuels such as natural gas and biodiesel are already expensive. Gasoline is very much used nowadays confirmed by the heavy traffic, therefore making gasoline prices more competitive is not a loss. It even makes more profit in the side of the fuel manufacturers.
> to provide funding for healthcare services and education - This is a government duty. Where do our taxes go? Genuinely for the basic needs and healthcare services and education are some of those.
> to discourage travel by automobile by making gasoline more expensive -Psychological reason; 'the higher the price, the less consumer use the product'. If you're in deep need, you can think of an alternative. So, what's the alternative? Walk or use a bicycle instead. In this way, you're not only helping the environment but also make yourself healthy.
> to fund highway repairs and other special projects - This is another government duty. This is where our other taxes go. It is distributed well for public service.
The fifth one is not applicable. It is supposedly "to encourage the use of alternative modes of transportation" not discourage. Walking or riding a bicycle is the best alternative to avoid air pollution. It is also a good exercise which is beneficial for your health.