Don't deduct commuting costs, but ...
The cost of getting to and from your workplace is never deductible. Taking public transportation or driving to work is a personal expense, regardless of how far your home is from your office.
And no, you can't deduct commuting expenses even if you work during the commute.
But you might be able to deduct some commuting costs if you work at two places in one day, whether or not for the same employer. In this case, you can deduct the expense of getting from one workplace to the other.
You also can deduct some expenses related to other work-related travel, such as visits to clients (current and potential) and out-of-office business meetings.
If you're self-employed, these expenses would go on your Schedule C or C-EZ.
If you're an employee, travel costs must be claimed as unreimbursed business expenses. As such, your business and other miscellaneous itemized expenses must exceed 2 percent of your adjusted gross income.
Whatever your business travel situation, be sure to keep good records.
You also could encourage your employer to establish a commuter savings account program. This employee transportation fringe benefit lets workers use pretax dollars to purchase mass-transit passes and pay for parking near work.