Having recently helped my mom find alternatives to driving her own car, an article in the paper today caught my eye.  http://www.tricityvoice.com/articlefiledisplay.php?issue=2011-10-14&file=Driving+++TCV.txt  Written from the perspective of an elder care provider, the wisdom and compassion in the article can be quite helpful.  For example:
***We all equate the act of driving to being free and independent. In talking with our parents about driving, we need to be respectful and understand that this is a transition for all parties involved.
***Have a checklist available that encourages open discussions about:
1) Yearly vision tests
2) Annual hearing tests
3) Effects of medication
4) Changes in their range of motion and strength during driving
5) Memory concerns
6) Driving the right car 
7) Buying the right products for your car, i.e., bigger rearview mirror (check out (www.disabilityproducts.com)
8) Alternatives to driving, i.e., offer rides, pay for public/private transportation.