Porous asphalt as a road surfacing material has been under test by TRL since 1967, but the use on more heavily trafficked pavements needs to be evaluated. Trial sites carrying moderately heavy traffic on the A38 and M1 have been monitored on behalf of the Highways Agency. On the A38 at Burton (traffic flows on two lanes of 3,600 cv/l/d and 475 cv/l/d), the trial compared the use of different binder contents and the suitability of certain binder modifiers to retain the binder without drainage. On the M1 at Wakefield (traffic flows on three lanes of 4,565 cv/l/d, 1,320 cv/l/k and 40 cv/l/d), the trial compared different European gradings and investigated the possibility of using precoated chippings in porous asphalt. On the M40 in Oxfordshire, the trial of porous asphalt overlaying jointed concrete was monitored. On the M4 at Cardiff (traffic flows on the three lanes of 3,300 cv/l/d, 920 cv/l/d and not recorded), the site has been monitored on behalf of the Welsh Office. The results are discussed and conclusions for the use of porous asphalt drawn. (A)

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