Just that really. A friend has done a lot of damage to her ankle and is in plaster up to the knee. She's reasonably mobile on her crutches now she's had some practise and she does a desk job. She feels she's well enough to work, but she can't drive to get there.
It's possible on public transport, but not easy, will take much longer than driving (approx. 1.5 hours v 20 mins) several changes, some walking and be expensive, as the last bit would involve a taxi. What would you expect your employee to do?