Download TTCI report: user guide for variable charges model

EXECUTIVE SUMMARY
TTCI(UK) Ltd., under contract to Network Rail, has continued to develop the
methodology for calculating variable usage charges for track access. This report
reviews the existing methodology before describing a new methodology. The new
methodology accounts for the variable usage costs arising from tangential forces
between the wheel and the rail. Sensitivity studies on both the existing and new
methodologies are described. Detail is given on applying the new methodology to
routes rather than the network in total. This report builds on earlier work1 and leads
to a final set of proposed variable usage charges for Control Period 4 (CP4). These
charges are published separately.
The sensitivity study shows the existing methodology, based on vertical
forces, is very sensitive to the assumptions used to derive the charging formulae. The
new methodology, in contrast, is relatively insensitive to its assumptions.
A full revision of the existing methodology is recommended. This should
result in state-of-the-art damage models calibrated to the latest service data. The
review and calibration should be fully documented and traceable. The revision should
be completed in time for Control Period 5.
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