A time–distance diagram is generally a diagram with one axis representing time and the other axis distance. Such charts are used in the aviation industry to plot flights, or in scientific research to present effects in respect to distance over time. Transport schedules in graphical form are also called time–distance diagrams, they represent the location of a given vehicle (train, bus) along the transport route. In project management, a time–distance diagram (also called time-chainage diagram, time–distance chart, time-chainage chart, time–location diagram, time-location chart, March chart, location–time chart, orthogonal diagram, line of balance chart, linear schedule or horse blanket diagram), is a method of graphically presenting a time schedule for all types of longitudinal projects such as pipeline, rail, bridge, tunnel, road, and transmission line construction. Activities in time–distance diagrams are displayed both along a time axis and along a distance axis according to their relative linear position. This allows showing not only the location of the activity but also the direction of progress and the progress rate. Activities can be presented as geometrical shapes showing the occupation of the work site over time such that conflicting access can be detected visually. Different types of activities are differentiated by color, fill pattern, line type, or special symbols. A symbolic drawing along the distance axis is often used to improve the understanding of the time–distance diagram. The advantage of a time–distance diagram is that it nicely shows all visible activities along the construction site on a single diagram. Layout A time–distance diagram is a chart with two axes: one for time, the other for location. The units on either axis depend on the type of project: time can be expressed in minutes (for overnight construction of railroad modification projects such as the installation of switches) or years (for large construction projects); the location can be (kilo)meters, or other distinct units (such as stories of a high-rise building). Normally, the time axis is drawn vertically from top (start of project) to bottom (end of project), and the location axis is drawn horizontally. The direction of the chainage is usually chosen with consideration of geographical position of the project, with the numbers either increasing or decreasing. The location axis is often enhanced with a schematic of the construction project. Other, location-specific information (aerial photos, cross-sectional views) can be added to enhance the visualization of the work site. A legend explaining the meaning of the