Your commuting costs aren't deductible. So transportation costs become deductible only if you're traveling outside your home territory or after you get to your first work location and before you get to your last work location.
E.g., you live in Seattle and normally work in Seattle, you need to be driving to outside the Seattle greater metro area in order to have deductible transportation costs... or you need to first commute from your home to your first work location.. and then further travel during the day becomes deductible... up until the point you get back to home office or last work location... and then driving back home begins your commute home.
BTW, probably transportation costs aren't very deductible if you're an employee. You need to itemize and transportation expenses for a job would only be deductible if your total miscellaneous itemized deductions exceed 2% of your AGI.
