7 Conclusions
Roadside concentrations of benzene and 1,3-butadiene have been estimated for future years. A comparison between these estimates and equivalent concentrations chosen to represent the National Air Quality Strategy Objectives has shown that national policies are likely to deliver compliance with these objectives at all major road links well before 2005. All but two road links are expected to comply for benzene by 2001, with all roads complying by 2002. For 1,3-butadiene our analysis suggests that only one link will exceed the objective in 2003, with all links complying by 2004.

Estimates of roadside benzene concentrations have been made in the context of complying with the target value of 1.0 ppb. The number, and location, of exceeding road links has been estimated, and scenarios assuming the implementation of hypothetical emissions reductions have been considered.

It is likely that considerable emission reduction measures, on top of those considered as business as usual, would be required to meet this target concentration by 2010.