Tool to manually detect ratruns

A very simple idea that would help me A LOT. Be able to place a single marker on the map and color the upstream / downstream roads in two different colors (like blue & red). Have a slider to increase or decrease the distance (either counting in length, or in intersection nodes).

Use case : I see too many traffic in a street but don't know where they come from (or where they would go). When I'm doing some scouting in the city, I would follow the cars and understand each branching. LTN could help me do that way faster.