The IRS recognizes that if you are out of town for business, that you will incur expenses for travel, meals and incidentals. Rev Proc 2011-47
There is a method to simplify the computation for these expenses on your income tax return for self-employed individuals and employees
Substantiating these expenses is also easier. Using this system you are establishing that you are out of town for business, thus you do need to substantiate where you were, when you were there and why you were there as opposed to substantiating each individual expense.
It is also important to note that if you deduct travel, meals and incidental expenses using this method, you have to be consistent.
There is a different rate for high-cost and low-cost travel areas, but the standard rate for those in the trucking industry, for 2014 is $59 per day.
Because this method of substantiation is easier, it is generally preferred.