Last weekend's mid-air collision over the Hudson River has focused attention on crash-avoidance systems utilizing GPS and ADS-B technology. Testing in Alaska has shown that such technology can cut the accident rate by nearly 50%, and has proven to be very successful in an area where conventional radar is not an option. Some experts say that such a system would be effective in areas such as the Hudson River corridor only if all planes were required to install the necessary equipment, and doing so can cost about $15,000 per aircraft. The FAA is moving ahead with installation of ground stations for the technology, and has considered requiring the technology for some planes. At this point, statutory FAA deadlines for widespread installation are set years in the future.