I prefer 4 sec rule( the most likely).
Sorry...
120 Kmph- in 4 sec you travel 13.33 meter.

100 Kmph- in 4 sec you travel 111.1 meter.

80 Kmph- in 4 sec you travel 88.8 meter.

60 Kmph - in 4 sec you travel 66.6 meter.