When a section of track is required for maintenance and trains cannot run, it is handed over by the operators to the engineers, who take "possession". Special protective measures are used to prevent access by unauthorised trains. When the track is returned to the operators, the engineers "give up possession".
" class="glossaryLink ">占有规划系统——管理国家工程和通行要求（财产、工地、临时限速）的预订和记录过程。
