Go to
http://www.discoveryowners.com/cginfolinks.htm This is part of a web site for Discovery Motorhome owners. It has several
Streets & Trips POI overlays including Wal-Mart (with and without fuel), Sams Club (with and without fuel), Cracker Barrels, Golden Corrals, Pilot Service Stations, Flying J Service Stations and a lot more, including three (I think) separate height overlays. They're in DeLorme, S&T, CoPilot and .txt format. I do not know how often it's updated but, just off the top of my head, I doubt that bridge clearances change much.