  The societal impact of traffic is a long-standing and complex problem. We
focus on the estimation of ozone production due to vehicular traffic. For this,
we couple a system of conservation laws for vehicular traffic, an emission
model, and a system of partial differential equations for the main reactions
leading to ozone production and diffusion. The second-order model for traffic
is obtained by choosing a special velocity function for a Collapsed Generalized
Aw-Rascle-Zhang model and is tuned on NGSIM data. On the other side, the system
of partial differential equations describes the main chemical reactions of
$\mathrm{NO_x}$ gases with a source term provided by a general emission model
applied to the output of the traffic model. We analyze the ozone impact of
various traffic scenarios and describe the effect of traffic light timing. The
numerical tests show the negative effect of vehicles restarts on
$\mathrm{NO_x}$ emissions, suggesting to increase the length of the green phase
of traffic lights to reduce them.
