Abstract：Research purposes: For re － using the idling state － own assets，the existing underground facilities are used for the some urban rail transits． As the track spacing is small and it is difficult to increase the track track spacing，the existing track spacing has to be reserved，but the relative code requires that the track spacing of the single junction track should not be less than the certain value． The defence tunnel was used for the first phase project of Harbin rail transit and its track spacing was determined as 3． 4 m due to the limitation bounds． According to the requirements，the single junction tracks with 3． 4m track spacing were installed in the two existing stations． At that time，there was a little experiments of designing，laying，operating and repairing the single junction track with small track spacing． Therefore， besides being necessary to research the security of the junction track structure，it was necessary to analyze and research the derail and its risks of the train at the different running positions to ensure the train safety．
Research conclusions: ( 1 ) When the train passes through the single junction track with small track spacing，the otation angle of the bogie on worst position was in the allowable range of the bogie structure property． The rotation angle and stroke of the train couple on the worst position were in the allowable range of the train couple structure property． ( 2) The train speed did not exceed the 20 km/h when the train run on the single junction track with 3． 4 m track spacing in side direction without passenger． The train speed did not exceed the 15 km / h when the train run on the single junction track with 3． 4 m track spacing in side direction with passenger．
徐彩彩 刘道通 田苗盛. 小线间距单渡线安全性研究[J]. 铁道工程学报, 2012, 29(2): 72-77.
XU Cai － cai，LIU Dao － tong，TIAN Miao － sheng. Research on Security of Single Junction Track with Small Track Spacing. 铁道工程学报, 2012, 29(2): 72-77.
China Railway First Survey and Design Institute Group Ltd． Planning of Lanzhou Urban Rail Transit Network ［R］． Xi’an: China Railway First Survey and Design Institute Group Ltd，2010．
2012, Vol. 29 
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