TTS Initial Review - Review of survey methods

The review studied the current use of automated road condition surveys in Europe and the rest of the world from experience, literature searches and electronic communication, and hence highlighted where the UK could usefully learn from experience outside the UK. A brief consultation exercise with a limited number of key experts in the field of local road maintenance and road surveying techniques was conducted to confirm the initial requirements from TRACS Type Surveys (TTS). The requirement for the final output of the project was a brief but comprehensive report covering all aspects of the review and specifically identifying the requirements for the introduction of the new surveys on non-principal roads in 2005/06 and on all local roads in 2007/08. TRACS Type Surveys (TTS) have been introduced by the DfT on the Principal Road Network (PRN) in April 2004, and are to be introduced on the non-Principal Road Network (non-PRN) in April 2005. No evidence was found that the use of automated condition surveys on local roads had been researched extensively abroad. The consultation with UK based experts found no entrenched opposition to the principle of TTS, but there was strongly held concerns regarding the current capabilities of the technology and the proposed timescale for introduction on the non-PRN. It was determined that in order for TTS to be acceptable to local maintenance engineers the surveys must be able to identify rutting, cracking, surface and edge deterioration as a minimum. The data analysis exercise has shown that the presence of edge deterioration cannot be simply derived from TTS measurements such as cracking, rutting or profile variance, as no strong correlations were observed between these parameters and the visually observed edge deterioration. Analysis of the data has shown that the TTS detection of cracking is consistently lower than the visual. The data comparison has shown that there are distinct differences in the level of accuracy and sensitivity of visual and TTS rut measurements, with the visual surveys displaying less sensitivity to small changes in the severity of defects, and tending to assess pavement subsections as being more defective than the TTS surveys. The review also concluded that there are currently insufficient accredited survey vehicles available for performing routine network wide surveys of the non-PRN, and raised the idea of introducing an accreditation procedure for vehicle operators and drivers in addition to the accreditation procedures applied to the vehicles