Abstract. Polymer modified asphalt mixtures have usually been used in wearing courses in order to improve both crack growth resistance and rutting performance where temperatures, vertical stresses and shear strain levels are more severe. Nonetheless, the need for either thinner yet high-performing wearing courses or ever-increasing durability provides the motivation for using higher polymer contents in the wearing course of bituminous pavements.Therefore, instead of the conventional use of 2-3% styrene-butadiene-styrene (SBS) in polymer modified binders (PMB's), the resort to higher SBS contents in the range 6-7% allows for a phase inversion in the PMB microstructure: the swollen polymer becomes the continuous phase in which asphaltene nodules are dispersed. This significant change in PMB microstructure brings about significantly higher performances. Besides, some other benefits may be related to the possible layer thickness reduction: less natural materials (aggregate, bitumen) used, less resources required for construction (man-hours, emissions during transport and laying) and, overall, cost saving.Microstructure, both empirical and rheological characteristics were investigated in laboratory for two different PMB's with very high SBS content (referred to as Biprene ® or Orthoprene ® ). In addition, in-situ testing was carried out: a brief follow-up of the highly trafficked Millau Viaduct surfacing (constructed in France in 2004) where this type of PMB was used, is in particular proposed.The paper illustrates that the proposed innovative highly modified bituminous mixes may be from now on potentially considered as a relevant solution for sustainable longlife and high-performance overlays, needing only rare surface maintenance.