Responding to recommendations from Canada's Transportation Safety Board after at least two low-visibility landing accidents, Transport Canada will increase the minimum visibility required before beginning an approach from the current 1,200 feet (370 meters) to 1,600 feet (500 meters), effective December 1. The visibility measurement can be made by a sensor or by a qualified observer if a visibility sensor has not been installed or is out of service. The regulations have been amended to prohibit commercial operators, including air-taxi services, from beginning an approach under conditions where a successful landing is unlikely. However, the rule will not apply to operators and crews already approved to lower visibility limits at specified runways. Transport Canada stated that the new rule will help harmonize Canadian regulations with international standards. The amendments will be published on September 20 in the Canada Gazette, Part II.