Well, you could purchase some land next to the freeway, get planning permission to construct signage on that land, comply with all the regulations regarding that signage which will double your construction costs and then put up whatever sign you want, knowing it can still be forced to take it down anyway if it breaks any trade, advertising or defamation regulations.
Or you could just save the hassle and use an ad agency who have already gone to all that trouble for you and won't post ads they know break the regulations.
Also, just quickly on defamation, if you want to say something negative about a company you'd better have extremely strong court admissable evidence that what you are saying is 100% true otherwise not only will your billboard be taken down but you could end up with a multimillion dollar lawsuit against you. Don't just jump on bandwagons know what you're talking about first.
Of course you can provide the ready to go digital art to a billboard company, I believe the cost of a freeway side sign in the neighborhood of $10,000+ month. Freeway side sign space tends to be locked up, someone interested in your cause with the land would probably have to go through a lengthy permitting process.
It's extremely unlikely that you could manage such a thing for free or cheap, making at an official cause that collects donations is more typically the way such publicity would be funded.
Jake is right.
you might see some space available on billboards that has been vacant for awhile, and approach them from a public service message point of view, that has some controversy in it.
but keep in mind, somebody has got to pay for the creation of your sign, whether it is on paper or digital.
find a non agy. billboard company. they might have one or two bill boards.
Why not go TV or radio it's cheaper then billboards.
This would a controversial billboard advert opposing a multi million $ corporation abusing workers and animals.
