So what is the best way to do this make my route and then go to the index and make sure none of these bridges are on my route?
If you only 13 6 any state or us highway should be fine Also any interstate The town roads and possible county roads are only problem and most counties have a county map you can download online some big cities have maps too.
You'll usually come across the biggest clearance issues in the northeastern section and in major cities. If you're 14ft or higher, you'll have issues elsewhere, but at 13'6, it's as stated above.
Pay attention, most bridges have there limits posted, not all. In San Antonio you can get into trouble off the interstate, but there posted.
You gotta try real hard to find a bridge under 13'6 unless you're right in the heart of the city. Everything else is well over legal height. The only time I had to run a goofy route from the city to W TX was with a 15'10 load.
I was delivering to South end of San Antonio and the underpasses going under the interstate were like 12'9 or close to it. you simply get back on the interstate, and try the next exit.
You're definitely overthinking. You'll get a feel for it after a while. You'll realize when you need to start watching more and being concerned by the area and what's around you. Don't make too big a deal of it... just read the signs and, if you're in doubt, atop and find out before you turn a hardtop into a convertible.
Just a note of caution. States can repave and actually raise the surface of the roadway several inches. Those signs and the information in the atlases are generally good but can be wrong at times. Just take note of new or fresh pavement on bridges that are close to start with. Also, I have discovered over the years that not all low clearance bridges are listed. These things can be confusing. I once was making a delivery in Texas and had to travel down a FM road off the network. I was told to be very careful and not miss my turn because there was a 9-foot bridge just past it. No mention of it at all in my atlas. Almost every tale of woe I hear coming from a driver trapped by one started by I was on a county or local road. I think that the now-famous video of that USA Truck was such an occurrence. Just be careful.