This report summarises the off-road research trials that were conducted to investigate the effect of graffiti on retro-reflective sign face materials and the different methods used to remove it. Sign manufacturers provided ‘normal’ sign faces and a set of sign faces with ‘graffiti resistant overlay film’ for the off – road trials. Signs were observed in darkness on a number of occasions to assess their loss of conspicuity and legibility after the application and removal of graffiti. Following these trials, recommended methods were made for cleaning sign faces and the results highlighted the improved ability of the protected signs to resist graffiti attacks. The results of this research led to further supplementary on and off-road research trials (PPR118), which observed traffic signs in situ and carried out further testing of the protective overlay films on the TRL test track.

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