algorithm - select the most fitting road by sketching lines on the map -

i have 2d road net data, contains lot of road points , lines link them. want select road(or several road) drawing lines on map, , lines can inaccurate, want find fitting road. there way achieve this? thanks.

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update:

it's not route searching problem, setting start point , end point , finding best route.

what want is, when user want select route on map, draw sketch line on map this:

and fitting route can found , highlighted this:

1) find roads link together

2) assign cost 1 road road link (only ones touching)

3) pick ones lowest cost - recursively