A method for updating speed limit, service stop location, or other attributes for road segments in a digital map (18) by extrapolating probe data from a subset of probe data which has been profiled to have originated from trustworthy probe traces. Probe measurements from a plurality of probes is collected and profiled against known information. From this, a subset of trustworthy probes is identified, comprising those probe traces which observe the known attribute of interest within an acceptable range for a majority of the driving time. These trustworthy probe traces are tracked during travel on other road segments whose attribute data is unknown or unreliable. A specification for the unknown or unreliable attribute on the other road segments can be extrapolated based on the collected information from all of the trustworthy probe traces as they travel that road segment. The digital map (18) can then be updated by setting attribute information in relation to the extrapolated behavior data. If atypical behavior is noticed in areas where there is high confidence of the particular attribute, then all probe measurements may be categorically rejected as unreliable.