They hate concrete

[tpenn 9]

By the docks at the north lumber mill, there is a separation where the grass stops and the concrete of the piers begins, last night I found the infected would simply run up to the edge of the concrete and stop. Made for quite easy pickings.

Again the location is the docks near the lumber mill along the north coast line, invisible barrier between concrete and grass.

[Adam (DayZ) 193]

This happens on all piers and is a limitation in the ArmA2 AI engine. Nothing we can do about it.