TPH
Initialism of trains per hour.
TPH: a measure of track capacity and scheduling density
TPH stands for trains per hour, a metric that expresses how many complete train movements a railway line or segment can handle during a 60-minute period. This is a practical capacity measure, not a theoretical maximum. It reflects the actual number of train slots a dispatcher can schedule given signal spacing, dwell times at stations, platform availability, and the operating rules of the network.
A single-track rural branch line might run at 4 or 6 TPH during peak hours. A busy metropolitan commuter corridor with frequent stops can push 20-30 TPH in each direction. High-speed trunk routes often operate at lower TPH (8-12 in each direction) because longer signal block lengths and higher speeds mean trains occupy track for longer periods. Automated urban light rail systems can achieve 40+ TPH on a single track because dwell times are minimal and headways (the gap between successive trains) can shrink to 90 seconds or less.
TPH as a planning constraint
Railway engineers and planners use TPH to determine infrastructure requirements. If a route needs to handle 24 TPH but the current signalling system only permits 16 TPH, upgrades are necessary: installing modern interlocking, reducing block lengths, adding passing loops, or in urban settings, moving to moving-block (CBTC) signalling. TPH also drives fleet sizing; a service pattern that requires 18 TPH needs enough rolling stock to maintain that frequency while accommodating maintenance schedules and driver rest requirements.
TPH is distinct from service frequency (trains per hour that actually carry passengers) because not all train movements are revenue services. Freight trains sharing passenger infrastructure, empty stock movements, and shunt moves all consume TPH capacity. A network that advertises 8 trains per hour to passengers might actually need 12 TPH capacity to support repositioning, maintenance access, and freight operations.
The term appears in timetables, track access documents, and railway operational statements. It is a hard number that regulators and operators use to define what a line can do, not what it should do. On most networks, achieving and sustaining 90 percent of theoretical TPH is considered excellent operational performance.