It can be accomplished by using an automated welding process. It took a really good local bridge shop several tries recently, and it was accomplished with a FCAW torch set up on a buggo track machine, with another procedure ran on SAW setup.

The reason it is there is to keep the heat input controlled. You can create a spreadsheet that will let you know when one weld pass exceeds 10% of the averages up to the last weld pass, or you can calculate each pass to figure it out. The best way is to just start out with the first pass, and use that to set your high and low values. If one pass exceeds the values, you need to make sure it doesn't exceed the averages of all the passes ran up to that point by 10%.

I have seen all but the last couple passes ran on a vertical procedure, only to have the operator accidentally bump the speed control button just enough to put one pass at about 15% over the averages, and ruin a days worth of work. 

Good Luck, even after running some decent procedures and getting the hang of it, you get to repeat it in 5 years if you continue doing that type of work.