My brother was a commercial trucker for years. He currently uses Streets & Trips for his personal travels. I've emailed him the link to this thread in case he might be able to help. I've never been a trucker so I wouldn't know what to look for.
I'm a professional computer guy so I do know how to drive a search engine pretty well. I found something that might work. This is a Canadian site but it looks like it's a North American product and is likely available many places. It's called CoPilot Truck Laptop. In my infinite ignorance it looks like it might deal with some of the things you are concerned about.
Here's another link with some more descriptions about the same program. It looks like the basic package comes with USA maps and there is a Canada map add-on if you drive up here. There is a link in the middle of the page for a downloadable fact sheet.
I have a Garmin iQue 3600 integrated PDA (Palm Pilot) and GPS. I can confirm that in the routing preferences you can select from a variety of things. As well as the usual car/Motorcycle, bicycle and pedestrian modes, you have these additional choices:
Truck
Bus
Emergency
Taxi
Delivery
Garmin's Street Pilot series has similar options. The new Nuvi series might also have them. They are standalone Nav devices, not laptop software.
I have Garmin's "nroute" program installed in my laptop using the GPS receiver from Streets & Trips. It also has the above options selectable in the routing preferences. I have Garmin's City Navigator North America map product installed on both devices. If there is anything I could do to test something for you I would be happy to. Like if you know of a particular route you are familiar with that I could test to see if it will cause you problems or do the right thing.
I've never used these preferences. I'm pretty sure there is nothing in the Garmin map data that will give things like low clearance. There may be info about commercial routes but you can be sure it will never be right up to date. The map data provided by Garmin's map suppliers is usually one to two years old by the time the map updates are available to buy. This will be true of most consumer map products, I think. But that's one of the things you are concerned about in the first place, yes?
I hope this helps get you closer to a solution.
...ken...