Vehicular Advertising for Independent Consultants

Had a chat with my wife last nite about the value of having a company logo/name/contact info on a new snappy vehicle as a mobile advertising medium. The big boys do it like Nerds On Site etc with PT Cruisers, Volkswagons etc. I’m an independent consultant and have been thinking about doing this for a long time. It’s difficult to get facts as to the effectiveness of this (ROI etc). Of course it has to be part of a larger marketing plan and I don’t expect it to suddenly get me double the work; it would be more for company name recognition and recall. So I turn to my fellow TR members for some anecdotal evidence. Is a nice-looking vehicle with catchy professional advertising on it effective for IT consultants?