Unit 2: Negative externalities associated with road pollution

The BBC reports that there are calls for a bypass in a town where nitrogen dioxide levels exceed national guidelines.

< http://www.bbc.co.uk/mediaselector/check/player/nol/newsid_7230000/newsid_7232900?redirect=7232908.stm&news=1&nbram=1&nbwm=1&bbram=1&bbwm=1 >

a) Explain why this pollution is an example of a negative externality
b) Evaluate the likely success of the bypass as a means of reducing the negative externality