Informal intervals

Since I didn't get out this morning, I made up my run by going out this evening. It was a beautiful evening.  Only a slight breeze and low 60s.   Wonderful.  I ran without music, so I decided to do informal intervals.  I would run at a comfortable pace for a block or two then run fast for a block, run to that street lamp up there, then to that corner, etc.  I was out for 30 minutes and averaged 10.9 min/mile or 5.5mph.