I know EXACTLY how you feel! I took off work when I changed jobs to take a day to take the bus as a practice run to go to where I had an interview later that week so I knew the answer to all the questions. I was always afraid that when I pulled the cord to ring the bell to get off, the bus driver would be angry and tell me I couldn't get off or be annoyed I was bothering him, etc. :-)

I was only cured when I took a train! to New York (from Washington, D.C.) by myself and spent the night alone in New York (turned out to be in a hotel for transients with yelling and breaking bottles, etc., extremely scary!) and when I came back the next day, in the middle of the convention I was going to, I couldn't stand the anxiety anymore I got "safely" back to Washington and suddenly felt like I could handle anything including taking any bus at all and "transferring" between buses, etc. which I'd been afraid of before (asking for a transfer, was again, afraid the bus driver would refuse or sneer at me or be angry, etc.). I was free of my bus/travel fear.

Take a practice run (or get yourself to a little ways away from your home and get home?) so you know the route. Just "ride" and get a sense of what it is like, how long it takes, etc. Usually bus routes are available on the Web and they have brochures, etc. and you can buy tokens or tickets, etc. ahead of time, etc. Go to your local library, they usually have the brochures in the reference section or can tell you where to get them.

Or, figure out something that would be "worse"/harder to do :-) and do that and the things "under" it will seem easier. Some of my fears was from the "requirement" that I do it, coming from "outside" me. The time constraint was an additional pressure. Relieve that by some practice runs and getting a little familiar with maps and prices, etc. Get on and go one stop (or until others are getting off?)

Maybe, if you have a "large" airport close enough you can go park in satellite parking and take the "bus" to the terminal and then catch a return one back to your parking lot? Make it fun, decide to buy a sweatshirt or something in a gift shop and "go get it" :-)

Do you know anyone/have a friend that is more scared than you are? That sometimes helps me, if I have to "act" brave and like I know what I'm doing or have to "take care" of someone younger than I am? Find a museum on a bus route (or near your T's office) and take a child there?