The most difficult element is reaching agreement on interoperability standards and protocols, Chertoff said, although cultural resistance has also played a role. "In some communities, not all, there are some long-standing cultural differences between different kinds of responders -- police, fire and EMS -- that have caused resistance to working together," he said.

For example, officials in some regions differ about whether their communities should drop the short-hand 10-code for a more universal language, especially since the codes can vary from place to place, he said.

Chertoff warned against comparing one region to another in the assessment, noting that Chicago had previously scored well in an assessment of interoperability in 2004. The reason the Chicago region as a whole rated in the lowest group in the latest ranking was because of the inclusion of all of Cook County, which includes 128 municipalities along with Chicago. "What the scorecard identified was these two entities, the city [of Chicago] and the county, needed to come together and work more effectively as a unified whole to building interoperability across the entire region," Chertoff said.

Chicago's Office of Emergency Management and Communications issued a statement shortly after the DHS evaluation was released, saying, "We strongly disagree with the results of this study, and feel the parameters of the study were inconsistent and limited." Chicago's own emergency communications have been lauded by DHS in the past, the agency noted, adding that the Chicago region was the largest urban area evaluated in the DHS scorecard.

"Surprisingly, technology capabilities were not included in the DHS evaluation of interoperability," the statement added. If that had been done, "it would have found the City of Chicago is fully capable of communicating with radios from Cook County and any of our 128 other municipal jurisdictions in the county." Further, a new IP-bridging technology helps the region communicate with equipment from New York to Los Angeles "and any jurisdiction in between."