One of the most common uses of CATs is for research and development. In this area CATs are probably more widely used than all other instruments combined to measure corrugation and acoustic roughness. This is appropriate as the CAT is a modern incarnation of a very much simpler trolley that was developed in Cambridge University Engineering Department in the 1970s to measure corrugation when no other suitable instrument was available.
The corrugation trolley from which the CAT was developed. This instrument was made at Cambridge University in the 1970s where it was used for corrugation research for more than a decade. A second instrument, supplied to British Rail Research, was used for acoustics research for more than 30 years.
A large number of CATs have been supplied to companies that develop products, such as friction modifiers, that reduce corrugation. The CAT is probably also the instrument of choice for universities and acoustics consultancies who undertake research on corrugation and wheel/rail noise. It is fundamentally important to these users that their results are unquestionably reliable. Most of the leading research groups in corrugation and wheel/rail noise worldwide use CATs. Their results are openly published at conferences, for example at successive International Workshops on Wheel/Rail Noise (IWRN) and in the peer-reviewed literature.
CAT measurements of both rails made between two stations on a metro system, showing irregularities in 30-100mm wavelength range (above) and 300-1000mm wavelength range (below), with one-third octave spectra. There is a highly resilient trackform in a right hand curve at 0.30-0.43km approximately and a conventional, relatively stiff trackform, over the remainder of the section measured, including a left hand curve of similar radius at 0.52-0.95km. The track is ground routinely, and these measurements were made shortly before grinding. The measurements show that the highly resilient trackform greatly attenuates long-wavelength corrugation (300-1000mm) but has relatively little effect on short-wavelength corrugation (30-100mm). This is extremely important for at least two reasons:
Longer wavelength corrugation gives rise to ground-borne noise and vibration. It was demonstrated by other measurements that these were very much lower on the resilient trackform.
Short wavelength corrugation is relatively shallow, so maintenance of rail on the resilient trackform is much less costly.