Regardless the ‘official’ dress code, you should always be presentable. You are not only representing yourself but the company you are hauling for.
Now, of course there are other things to consider, job related required clothing. Examples are steel toed boots, or rain and/or cold weather gear. Perhaps eye and hearing protection are necessary.
But outside of that it can be up to you to dress for success.
What kind of clothes truckers prefers
There is a common stereotype of jeans, trucker caps, and western boots. There is nothing wrong with that. Because clothing needs to be comfortable and practical for what you will be doing. But as times change so does the clothing of choice.
Remember you don’t want to wear tight or restrictive clothing, especially during a long haul. You want to be comfortable and relaxed (not too relaxed mind you). Clothing that will breath and is easy to care for, wash and wear.
Source: icclogistics.com
And, consider the unexpected; be prepared for any changes in the environment. Weather can change fast so always have a few extra things, even if you don’t think you’ll need it.
