Route measures may need to be updated from time to time, for example, when more accurate information has been obtained or the geometry of the route has been altered in some way.
Route measures are edited using the edit sketch in ArcMap. When editing route line features, the edit sketch is simply a shape that represents a copy of the route's geometry. Once you have made the necessary changes to the route measures, you finish the edit sketch. Finishing the sketch updates the feature geometry of your route including changes to its measures (m-coordinate values).
Realignment
Realigning a route is the act of defining a new course for a route. Once a route is realigned, you may need some portions of the route measures to remain unchanged, while other measures need to be updated. Because of this, it is possible to remeasure whole routes or portions of routes.
When you are defining a portion of a route to be remeasured, create a sketch to include only the geometry of the portion to be remeasured. Once the sketch has been created, use the Route Measure Editing sketch menu—just like you would if you were remeasuring the entire route.