Unirow calibration using the Fundamental Diagram


Unirows (count points on highways and motorways) used for measuring traffic condition, usually project the measured values onto the so-called fundamental diagram.

The fundamental diagram uses averages of detector measurements. Mostly q (count) and v (speed) are measured, from which k (density) can be calculated.

The traffic conditions are usually divided into 6 groups, from 1 (fluid traffic) to 5 (very dense traffic) and 6 (traffic disturbance, e.g. traffic jam).

The product "VS-Funda", which can also be used as a module of VS-pCoq and the VS-WorkSuite, allows on the one hand

  • Unirow parameterization in a graphical window,
  • Measured data evaluation.

The evaluation can happen

  • On data archives
  • Or online.

Calibration graphics

There are three different diagrams types in which two of the three values ​​(q, v and k) can be displayed. So the traffic engineer can work with the most appropriate view.

The next pictures show a measurement period with point clouds of the measured values ​​and, shown by colored arrows, the last ten consecutive measurements. The same measured values ​​are shown in all three views.



In determining the areas of traffic conditions, it is important to have insight into the chronological sequence of measured values.

Such an insight can be gained by sliding averages of the values, resulting in a display of "strings of pearls":

Result projection

The calibrated results can also be mapped onto simpler traffic conditions, e.g. three traffic conditions only: green (free flow), yellow (dense flow) and red (traffic jam). The next picture shows the number of vehicles per hour, colored by the corresponding traffic condition:

Use for online control

The module "VS-Funda" is also used in control projects, where each module is responsible for an individual measuring section. The results of some consecutive modules form together the status of a route section. The ensemble of the route section status can be used as input variables for a rule-based controller, for example for driving variable message signs.