How many feet ahead should drivers look on city streets?

Useless answer: All the way.

Good Answer:You need to be scanning your surroundings and a set distance is not how you should be watching.

The goal is to see as far down the street as you can see and any children, opening doors, and so on as you drive.

That distance is 12-15 seconds or about 1 1/2-2 blocks (500-700 feet)