PUPIL - Track Geometry Assessments

PUPIL analyses the measurement data (level, alignment, cant, twist, curve radius, etc.) captured by track geometry measuring cars. 

Then, using a representative selection of vehicle types, speeds and loading conditions that operate on a network, PUPIL prepares a simulation model to determine track forces, Y/Q safety against derailment coefficient and car body accelerations.

For each track section, all modelled vehicles are simulated as if running on the track section. The most critical configuration determines the safety factor relative to the limit values from euronorm EN14363.

Other assessment levels - such as Alert or Maintenance limits - can provide information for maintenance planning.

To support maintenance processes, PUPIL can also provide information on the cause of the exceedance. For example, an exceedance on maximum lateral track force could originate from an alignment defect 30 meters back.

The most frequently used method for assessing track geometry is the comparison (for various cord lengths) of the maximum amplitude of each measuring signals with a speed dependant limit value (for instance according to EN13848-5). The disadvantages is that this method does not include:

• The assessment of multiple defects on the same location, which is likely to be more critical compared to assessment of individual defects.
• The assessment on multiple defects after each other (cyclic top) resulting in strong oscillations.
• The influence of driving direction. The dynamic response e.g. when running on and off bridges heavily depend on the running direction.
• An assessment on the influence the shape of the defect has on the dynamic loads on the infrastructure, see below.

Traditional assessment methods assign equal severity to each of the above signals. From a vehicle track interaction point of view, however, there are large differences between the vehicle responses resulting from each signal.

As part of the track geometry assessment, expert judgements are needed for specific defects identified in the data.

Based on the limited information provided by traditional methods it can be difficult to determine the most appropriate action (such as a repair, a temporary speed restriction, or line closure). 

PUPIL provides additional information to help guide maintenance responses. The Vehicle Response Analyses, for example, can help determine if a defect still supports safe running conditions, or help calculate safe speed limits.