What is linear referencing and Linear Referencing Systems (LRS)? Simply put, it is keeping track of your roadway assets by tracking where they show up along a linear network. For instance, a traffic sign may be known to exist at a point 45.3 miles from the start of Highway 101. For transportation agencies that track hundreds of types of information about their transportation network, linear referencing is an integral part of their information infrastructure. It is the “where” of their information.
Linear referencing far pre-dates computers. The ancient Romans marked their roads with milestones. Well before computers, transportation agencies kept track of linear locations of their assets on spreadsheets. I am not talking about Microsoft Excel. I am referring to spreadsheet paper: dead-tree paper with lots of lines on them where transportation analysts meticulously scribbled down route names and measures for all the items they were tracking.
With the dawn of the computer age, spreadsheet paper was replaced with spreadsheet applications and eventually with various asset management applications. These applications developed as point solutions for safety, traffic, pavement, etc. As these applications were developed entirely independent of each other, they also developed independent solutions to linear referencing. As a result, linear referencing components such as route naming conventions and linear measurement conventions varied between each of these systems. This independent development gave birth to the problem of multiple Linear Referencing Methods (LRM).
The next stage of linear referencing development came with the development of Geographic Information Systems (GIS) or intelligent mapping. This made it much easier to view and spatially analyze linearly-referenced data. It also became the preferred method for maintaining the linear-referencing network. This gave rise to one centralized group being in charge of maintaining the network. Centralizing that effort was a timesaver but it was still up to the individual business groups to update their data to match changes to the network, a very big challenge.
This brings us to where we are now, at the dawn of the era of Single-Source LRS. Single-Source LRS provides one system that not only maintains the network but automatically updates the entire enterprise’s business data as well. This is not trivial. For every edit to the base network, say renaming a route, there can be hundreds of records of business data that need to be updated to match. So in a Single-Source LRS one edit by the user can result in hundreds of automated edits by the software. This is the type of force multiplier not often seen.