From the railway station to Ziwei City Garden is the No. 5 bus line in two directions. The dispatching station departs at regular intervals. Qingya walks on this line at a constant speed. She finds that every 6 minutes there is a bus catching up from behind. For her, every 4 (2/7) minutes there is a car coming towards her, so the dispatching station sends a car every few minutes?
火车站至紫薇城市花园是5路公交车双向对开的线路，调度站每隔一定的时间发车一次，清雅同学在该线路上匀速行走，她发现每隔6分钟就有一辆车从后面追上她，每隔4(2/7)分钟就有一辆车迎面向她驶来，则调度站每隔几分钟发一次车？
<result>5</result>