In this occurrence, the assignment crew consisted of a foreman, who was in charge of coordinating the switching activities, and an assignment helper. Including the locomotives, the assignment was 4537 feet long and weighed 9116 tons (Appendix A). Footnote 1 Locomotive CN 7230 was set up to operate using RCLS. The first car behind the locomotives was dangerous goods tank car UTLX 208275, which was loaded with a flammable liquid (UN3475). At the time of the occurrence, the assignment consisted of 2 head-end locomotives (CN 7230 and CN 207) and 74 cars (72 loaded and 2 empty cars). The yard is located in the Concord industrial district of Vaughan, Ontario, in the Greater Toronto Area ( Figure 1). On 17 June 2016, the Canadian National Railway Company (CN) remote control locomotive system (RCLS) 2100 west industrial yard assignment was performing switching operations at the south end of MacMillan Yard. There was no release of dangerous goods and no derailment. It rolled uncontrolled for about 3 miles and reached speeds of up to 30 mph before stopping on its own at about Mile 21.1 of the York Subdivision. However, the assignment continued to move. The assignment helper attempted to stop the assignment to prepare to reverse into track W100, in order to continue switching for customers. The assignment was pulling 72 loaded cars and 2 empty cars southward from the yard onto the York 3 main track in order to clear the switch at the south end of the Halton outbound track to gain access to the west industrial lead track (W100) switch.
On 17 June 2016, at about 2335 Eastern Daylight Time, the Canadian National Railway Company (CN) remote control locomotive system 2100 west industrial yard assignment was performing switching operations at the south end of CN's MacMillan Yard, which is in the Concord industrial district of Vaughan, Ontario.