If you have multiple signals moving down in parallel, your best option is probably circuit C from http://www.minecraftwiki.net/wiki/Redstone_Circuits#Vertical_transmission. If this pattern is staggered 1 block apart on each successive line, adjacent lines should not interfere with each other. This circuit has the additional advantage that the signal can be extracted at any height.

If you have multiple signals moving down in parallel, your best option is probably circuit C from https://minecraft.wiki/w/Redstone_Circuits#Vertical_transmission. If this pattern is staggered 1 block apart on each successive line, adjacent lines should not interfere with each other. This circuit has the additional advantage that the signal can be extracted at any height.