A data packet transmission system having a succession of stations each connected to two buses transmitting in opposite directions, both packets and time-slot requests has its capacity improved by means of a request-erase counter at each station for each bus, making possible more efficient use of time slots. Except for the different combinations of status and expectable occurrence, the queuing protocol known as DQDB, optionally is modified by D.sup.3 Q protocol, is used. For those ten situations where time-slot-request bit resetting (erasing) comes into play, status is defined by the state of certain counters while expectable occurrences are arrivals at a station's access unit of a time-slot that is empty or contains a data packet or a request bit and also the use, if any, made of the arriving time slot by the access unit of the station. The actions produced in those ten instances are in terms of setting or resetting a request bit and advancing, reducing or resetting contents of one or more counters.