What is a standard rate for freelance copywriting?

I have a business that produces custom publications (some of it content marketing -- newsletters, white papers, etc.) for businesses and organizations. It is full turnkey work usually, not just writing and editing, so I price most things on a project basis. It is hard to say exactly what is appropriate for the OP's client, because a mom & pop trucking company is different than a Fortune 500 company.

But if I ever charge for something written by the word, it starts at $1.25 a word (these are mostly big companies) and works its way up, depending on the client and the expertise needed for the work.

If you are billing your work out by the hour, reformed is right. Take into account not only what you get paid, but your overhead (supplies, electricity, equipment, etc., health insurance, etc.), and price it in.

I can easily hire a writer for a project, bill a client $150 an hour and pay a writer $75 an hour. So for your trucking company -- if you have low overhead, and you don't feel the need to pay yourself a premium for having had to market yourself and find the work -- if you are confident that you offer quality work, I'd consider a minimum of $75 an hour.

Remember, when you negotiate with someone you can always negotiate down (and they feel like they got something), but you can't negotiate up. So consider throwing out a number like $150 an hour, maybe, and be prepared to come down from there if you really want the work. Also, it usually works out best if you are good at estimating the time commitment and pricing it by the project, rather than giving an hourly rate. The sticker shock can seem like less that way, even though you are getting paid the same amount you would.