Where I live I have limited options with regards a route when running from my house without having to double back on myself. The loop I run was OK up until about 35 minutes running and 2 lots of 5 minute walks as that took me door to door.
My compromise was to accept that I will have to double back on myself, but if I do that while walking it does not affect the running. (OK, I know I may be bonkers, but it made sense in my head).
I set off from home in one direction, then after a while, turn and start walking back, then after a total of 5 mins walk, I start my run. I increased the distance each week before turning back. Once I reached the full 5 minute without turning around I stated doing a similar thing at the end of the run, running past my house before starting my cool down walk. That was a bit more difficult to judge so sometimes I get a bit longer or shorter cool down.
By my calculations, I should be able to get to about 48 mins of running plus my 2 x 5 minute walks and still start and end at my front door. At that point, other routes will fall within my reach without having to turn and double back while running (although I will have to come back along the same road, but it will be a loop at the far end and not an abrupt turn).