/tilos/what-is-time-location-scheduling/
Time-Location Scheduling — also known as Line of Balance, or by its older French name, the “chemin de fer” (railway) method — is a way of planning work that moves progressively along a physical alignment: a railway, a road, a pipeline, a water main, a tunnel. Instead of a bar for every activity against a calendar, you get a chart with time along one axis and distance along the other, and each activity becomes a single line showing where the work is and how fast it’s moving.
A short history
The underlying technique is generally credited to the Goodyear Company in the late 1940s, developed to schedule repetitive production-line manufacturing. The US Navy adapted it in the 1950s for shipbuilding and repeated facility construction. From there it moved into civil engineering: first onto genuinely repetitive work like identical houses on a housing scheme, then onto continuously linear infrastructure, where the “repetition” isn’t identical units at all, but a smooth, continuous progression along a route. That’s the branch of the method this section is about, and it’s the one TILOS was purpose-built for.
The problem with Gantt charts on linear projects
A Gantt bar for “track laying” tells you it runs from week 3 to week 11. It doesn’t tell you it starts at chainage 10 and reaches chainage 34 by week 11, and it doesn’t tell you that the ballasting crew, two weeks behind, is about to run into the signalling team working the same stretch. Once a schedule has a physical dimension, a chart with only a time dimension is missing exactly the information a site-facing planner needs to sequence work safely.
How a time-location chart works — reading it step by step
The horizontal axis is time. The vertical axis is distance — usually expressed as chainage, the running measurement along the alignment from a fixed start point. Each activity is drawn as a line from its start point (a time, a chainage) to its finish point (a later time, a further chainage). Take the simplest possible case: a single crew resurfacing one 10 km carriageway, start to finish, at a constant rate.
- The slope of the line is the production rate. Here it rises 10 km over 8 weeks, so the rate is 10 ÷ 8 = 1.25 km per week — read directly off the chart without needing a separate report.
- A steeper line means faster progress; a shallower line means slower progress. If a real activity’s line kinks partway through, that’s usually a mobilisation curve — slower for the first week or two, then settling into its planned rate.
- A horizontal segment means the crew has stopped moving through the chainage entirely. A genuinely vertical line would mean instant progress across the whole route in zero time — real construction activities essentially never do that.
Two activities’ lines crossing on the chart is an instant, visual warning that two crews are trying to occupy the same location at the same time — the kind of clash that’s very easy to miss buried in a list of Gantt bars. The Examples Library takes this further with a case where exactly that happens.
Line of Balance vs Time-Location Scheduling
The two terms are used almost interchangeably in UK infrastructure. Line of Balance is the older, broader term, developed for repetitive work generally. Time-Location Scheduling (and the French chemin de fer term) is the same underlying logic applied specifically to continuous linear alignments. In practice, most UK planners just call the chart itself a time-location chart, a time-chainage diagram, or a Line of Balance diagram.
Where it’s used
- Rail — renewals and new-build (track, overhead line, signalling), scheduled by chainage along the route.
- Highways — widening schemes and resurfacing, scheduled by lane-kilometre.
- Water & sewerage — trunk main and sewer renewal, scheduled by chainage between chambers and manholes.
- Oil & gas pipelines — cross-country construction, scheduled by weld or lay progress per kilometre.
- Tunnelling — TBM drives, scheduled by daily or weekly advance rate.
Where TILOS fits in
TILOS (Time Location Scheduling software) is the dedicated tool for building and maintaining these charts at a working level of detail: setting up the distance axis and sector profiles for the actual alignment, adding resourced activities, saving a baseline and updating progress against it, and exchanging data with Primavera P6 or MS Project. See TILOS vs Primavera P6 for how the two typically work together.
Ready to put this into practice on your own project? See corporate TILOS training →