What I suggest is a countdown pop-up when approach the turn the car, par example, when I receive "next 200 meters turn left..." Will pop-up a countdown that will be par example :

200 meters
150 meters
100 meters
...

10 meters

Turn left Now !!!

This will disperse the doubts when the 200 meters finished...

Such thing happened when aircraft approach landing, an automatic voice to the pilot says...

200 (meters high )
100
50