Car signage and graphics may be the most cost-effective and impactful form of advertising available to business owners. For a modest investment, a vehicle with signage advertises your services or products for as long as you operate the vehicle.
Vehicle advertising has been around for a very long time. Back before the ubiquitous combustible engine, even the wagons (covered and uncovered) of gospel shows, hawkers selling their cure-alls and tonics, troubadours, circus acts, wild west shows; and of course, cartage companies, hand painted their main marketing messages boldly on their carriages.
Possibly the first wide-audience mobile advertising adorned the sides of rail cars, promoting brand names such as Sears, Ford and others.
Hand-painting logos and other branding, imagery and lettering on vehicles was hard work, involving days of painstaking labour. There was no "Edit > Undo" back then. If you went outside the lines, you probably panicked and carefully daubed with a rag and turpentine. It wouldn't take much of a mistake to ruin hours, or even days' worth of work.
Just look at old Vancouver vehicle signs, and you'll see the skill, time and labour involved in creating hand-made vehicle graphics...