At some point during a large incident, any agency will reach a point where they find their resources overrun by needs. For example, the Port Authority Police could not schedule staff as if a September 11 attack would occur every shift. There is always a balance struck between readiness and costs. There is conflicting data but some sources suggest there may have been 2,000 to 3,000 workers involved in the rescue operation. It would be rare for most agencies to see an event where there were that many people to be rescued. There is some level of confusion present in any large incident. The National Institute of Standards and Technology (NIST) asserts commanders did not have adequate information and interagency information sharing was inadequate. For example, on September 11, persons in the New York City Police Department (NYPD) 9-1-1 center told callers from the World Trade Center to remain in place and wait for instruction from firefighters and police officers. This was the plan for managing a fire incident in the building and the 9-1-1 center staff were following the plan. This was partly countered by public safety workers going floor-by-floor and telling people to evacuate. The 9/11 Commission report suggests people in the NYPD 9-1-1 center and New York City Fire Department (FDNY) dispatch would benefit from better situation awareness. The Commission described the call centers as not "fully integrated" with line personnel at the WTC. The report suggests the NYPD 9-1-1 center and FDNY dispatch were overrun by call volumes that had never been seen before. Adding to the confusion, radio coverage problems, radio traffic blocking, and building system problems occurred inside the burning towers. The facts show that much of the equipment worked as designed and users made the best of what was available to them. Typical of any large fire, many 9-1-1 calls with conflicting information were received beginning at 8:46 am. In addition to reports that a plane had hit the World Trade Center, the EMS computer-aided dispatch (CAD) log shows reports of a helicopter crash, explosions, and a building fire. Throughout the incident, people at different locations had very different views of the situation. After the collapse of the first tower, many firefighters in the remaining tower had no idea the first tower had fallen. A factor in radio communications problems included the fact that off-duty personnel self-dispatched to the incident scene. Some off-duty