Hello there !
"They should at least fix the traffic (embouteillages/bottlneck?) which has been polluting the air and causing embarrassing road rages."
In french, it will give something like :
"Ils devraient au moins régler le problème du trafic, qui pollue l'air et provoque des comportements violents."
Here I took the liberty to translate "fix" by "régler le problème", as the closest equivalent to this is "réparer", which is out of context here.
"Embarassing road rages" is quite funny ! You can't translate that directly. I mean, in case of traffic jam, people don't go outside cars and randomly fight, right ?
So i translated that by "comportement violents" (violent behaviours).
Good luck with your exercise !