Converting Calculated headways to signal spaces.

[KenD]

Whatever the value is, this is the closest spacing of 3 aspect signals and therefore lowest possible headway distance is then derived by:
double signal spacing + sighting distance + train length + overlap length. Convert this to headway time by multiplying by the timetabled speed of the train (i.e. could be the maximum train speed but may be less). Then, as you have said, you need to ensure that there is an appropriate % contingency to arrive at the timetabled headway.

Shouldn't the value be divided by the speed of the train?