If one is sitting in a vehicle and sees through the window that there is waste on the street, as long as there is no foul odor entering the vehicle it is permitted to recite a Davar Shebikedushah, since there is a glass window in between. This can be applicable to a garbage truck with a smell from rotting garbage riding in front of your vehicle.

If one is walking in the street and a garbage truck with a smell from rotting garbage is standing or riding in front of the person, one may not think in learning or recite a Davar Shebikedushah.