Reduce width of a loop type model I have a sort of loop type model(something like racing track) where there are 2 paralel curve-typed vertex loops. They're connected together like this
(simplified image):



Red lines - edges of outer loop
Yellow lines - edges of inner loop
Magenta lines - the connections between loops
Green dots - vertices
Blue dots - joint middle points(not actual model data, just imaginary thing for explanation)


What I want is to scale the magenta edges down(move green vertices which are joined with the magenta edges closer to each other) without changing the position of the blue points(the place where the magenta edges are or the place where the 2 connected vertices are). I could do it manually(select each 2 vertices and press S, .7, for example), but it would take a lot of time. Is there any automated way to do it?
Edge Slide

The idea is to pick one of the boundary loops and slide it by pressing GG in order to make it move next to the other other.



In order to use the middle point lines as a pivot, you should create a third loop in the middle with for example Ctrl+R....



...and then slide each loop by the same factor.