4.5.4 Percent Time-Spent-Following
Percent time-spent-following (PTSF) is expressed as a percentage. Per the HCM, PTSF is defined as “the average percentage of travel time that vehicles must travel in platoons behind slower vehicles because of the inability to pass.” A platoon consists of vehicles or pedestrians that travel together as a group, either because of traffic control devices, roadway geometry, or other factors.