1. A method for updating certain attribute specifications for road segments in digital maps, by extrapolating probe data from a profiled subset of trustworthy probe traces, said method comprising the steps of: accessing, by a processing device, a digital map having at least first and second road segments stored on a storage medium, each of the road segments having a common attribute with a respective attribute specification, the specification for the first road segment attribute being known and the specification for the second road segment attribute being unknown or unreliable; obtaining, by the processing device, data reported from a plurality of probes tracking across both of the first and second road segments, the reported data including attribute information; matching, by the processing device, each probe trace to a specific road segment in the digital map for a given time while collecting its reported attribute information; calculating, by the processing device, a correspondence value between the known attribute specification of the first road segment and the reported attribute information for each probe trace matched to the first road segment; defining, by the processing device, a correspondence threshold for the known attribute specification; identifying, by the processing device, from among the plurality of probe traces matched to the first road segment a subset of trustworthy probe traces whose calculated correspondence value does not exceed the correspondence threshold; collecting, by the processing device, the reported attribute information from each trustworthy probe trace when matched to the second road segment; extrapolating, by the processing device, an attribute specification for the second road segment based on the collected attribute information from all of the trustworthy probe traces when matched to the second road segment; and updating, by the processing device, the stored digital map by setting the attribute specification for the second road segment in relation to the extrapolated attribute specification.