Algorithm 1 . Route choice policy.

Data: R, a set of n road Ids considered within the emissions-controlled area. S, a sorted list of

roadIds according to their RSD ${}_{roadId}$ readings. V ${}_{edges}$, a set of edges that comprises the

current vehicle’s route.

Result: Vehicles select less polluted routes based on AQE alert messages.

/* Public Infrastructure Premises.

1 for $eachroadId\in R$ do

2   update RSD ${}_{roadId}$ reading

3   compute avrg(RSD ${}_{roadId}$);/* Updated every 15 minutes.

4   update S list;/* Tuple (roadId, avrg(RSD ${}_{roadId}$))

5   if $avrgRS{D}_{roadId}>AQG$ then

6     sort S list;/* S list is sorted in ascending order according to

average (RSD ${}_{roadId}$) entries.

7     generate AQE message;/* AQE messages include roadId, roadLoc,

and sorted S list.

8     RSUs broadcast AQE messages;/* I2V communication.

9   end

10 end

/* Vehicles Premises.

11 if AQE message received then

12   if $Nod{e}_{CurrTime} - AQ{E}_{Timestamp}>TThreshold$ then

13    from AQE message GET roadId, roadLoc, S list

14    if AQE roadId $\in V_{edges}$ then

15     recalculate vehicle route;/* Less polluted road is considered in

the first place, and so on; see Fig. 3.

16    end

17    if $AQ{E}_{hops}\le Ma{x}_{hops}$ then

18     forward AQE message/* V2V communication; see Fig. 2.

19    end

20   end

21 end