As a newcomer to the forum I've only just seen this thread. Earlier SteveHB (19 March 2014) queried why some drains had "TRAFFIC ->" cast on them. It really did mean to align them in the direction of the vehicular traffic. The way narrow wheels rolled over a series of narrow slots and didn't go down the gaps. Not an issue with modern cars, but I well remember the infamous Royds type covers around Millhouses. If you didn't spot them in time on your bike the front wheel went down and stopped dead. The result was always scabbed knees and elbows!