cr0sh:
I've never messed around with line followers, but I think that the increased number of sensors also relate to how to sense when the vehicle crosses over a line "perpendicular" to the line being followed (so it can be ignored in preference to the actual path being taken).
Yes, I was thinking that too. I'll be testing that thinking....
Also, with more sensors, you can tell how far away the robot centreline is from the line, and use that fact to dictate the best way to get back on track, say in terms of speed and angle of approach.