Snail's pace

It rained heavily last night, and that always brings out the snails. As I walked down our lane this morning, there they all were, purposefully crossing the lane and, in snail terms, going like the clappers.
 
The odd thing is, they were all going in the same direction. I wonder why. What was it about the other side of the lane that drew them, and how did they know which way to go?