1. One or more computer-readable media, not signals per se, having computer-executable instructions embodied thereon that perform a method to deliver routing information, the method comprising: receiving a request for directions at a routing engine; generating routing information in response to the request for directions received by the routing engine; transmitting the routing information generated by the routing engine; receiving user modifications to the routing information at the routing engine, wherein the routing engine conflates the user modifications to a routing network having a plurality of routes and modifies a weight associated with one or more routes based on the user modifications to make the user modifications to the routing information available to future requests for directions received by the routing engine; generating a notification that the user modification is incomplete when the user modification does not completely connect with the routing information generated by the routing engine; receiving additional information from the user that clarifies the user modification in the response to the notification, wherein the additional information includes a period of validity for the user modifications; generating, by the routing engine, updated routing information based on the user modifications; receiving, by the routing engine, a subsequent request similar to the request for directions; and in response to the subsequent request, providing both the routing information and the updated routing information, wherein providing both the routing information and the updated routing information further comprises: verifying that a count associated with client devices that transmit modifications similar to the user modification is above a specified threshold before providing the updated routing information that includes the user modification as a shareable modification.