According to my latest internet searching I have come across a few items but the ones that seem to work are as follows:
The red brick road is supposedly where the Munchkin Army marches in from so the idea is it may lead to the barracks. There is also mention of Glinda heading in that direction(towards the red brick) when she leaves. Another rumor is that there was a death on the set and this was a memorial tribute.
On a more important note however I was wondering who else remembers those hand puppets that were included in boxs of clothes washing detergent back in the 1960's. I had all the important ones...the scarecrow, dorothy, the lion and others. Did anybody else have them and does anyone still have them? Oh the hours of fun I had with those