I interviewed Dr. Fredric Schroeder, president of the National Blind Association. He stated that three big fears exist for the blind population:
1) When people walk behind them instead of in front of them
2) Objects at eye level
3) Changes in elevation, specifically curbs.
Curbs are especially dangerous to the blind as their cane is not always able to detect those changes in elevation. The majority of the blind population is elderly and if they fall due to not detecting curbs it can cause a fall.
People with bifocals or deteriorating vision also have trouble seeing curbs.