Advertisements Driving Up Emissions

While out running errands the other day, I saw a one of those trucks that drives around as a mobile billboard. I have seen them a few times before, usually in more major cities. Now that I am taking this class, and have a broader knowledge of energy and environmental concerns, seeing that truck make me stop and think... "Are you kidding me?" Who, with all of the global warming and carbon emission issues, would give the go ahead to an idea for a vehicle that drives all day solely to promote a product?
I found an article out of Canada that shows that people are raising those same concerns with a new fleet of advertising trucks that moved into town. The trucks drive about 100 km a day over 11 hours, five days a week and produce 850 kg of emissions per month. Crazy, right? But in the company's defense, they say that they are off setting their carbon emissions by using biodiesel. Another thing that works in their favor is that the trucks aren't driving around aimlessly. The trucks are used to deliver goods for food banks and other types of non-profits that would be using trucks anyway, they just make use of the valuable blank space on the sides of their trucks.
I agree with utilizing the blank space on the sides of delivery trucks for advertising, it makes sense economically; the space is just there. However, I have seen mobile advertisements that were purely billboards on the flat bed of a truck that had no room to haul any items, and that I can not get on board with. I understand the incentive, but ultimately it is a frivilous way to get your product seen at the cost of the environment. So if the truck is purely used as an advertising vessel, I feel there is something very wrong with that.