If you want people to go to work don't punish them if they live in the countryside or have bad bus services or its expensive on the train etc.
Most people drive to work because Public Transport is unreliable, expensive, inflexible, can be dangerous at night and doesn't do door to door.
Quite a lot of people at my work cycle to work if they live within about 10 miles of the office so they do their bit.
Don't punish good intention by hitting the company with the tax which they will pass onto the employee. Make work pay not mean paying out more!