In the next 20 years the number of elderly drivers -- persons 70 and over -- is predicted to triple in the United States, and statistics show that older drivers are more likely than younger ones to be involved in multi-vehicle crashes, particularly at intersections. It was just such a fatal accident between a Dallas teen (Katie Bolka) and 90-year-old woman that inspired Texas to pass Katie's Law last year. The law, a year old this month, requires motorists age 79 and older to renew their licenses in person and undergo a vision test. Starting at age 85, drivers must renew every two years, instead of every six. If DMV personnel observe shaking hands, an elderly driver having trouble answering questions or other red flags, they can require a road test or ask for input from on-site medical examiners. Although it is still too early to draw conclusions about the law's effects, preliminary figures from the state Department of Transportation are encouraging.