Comparison of methods for evaluating airport pavement roughness

The correct and timely assessment of the airport pavements surface quality is fundamental to verify the presence of any irregularities that could be detrimental to aircraft operations. Furthermore, a rough runway can increase the maintenance costs of both pavements and aircrafts landing gears, due to the increment of dynamic loads and fatigue phenomena on airplanes structural elements, reducing their service life. Nowadays, the maintenance budget available by airport agencies is very restricted, thus, it is necessary to define properly the type and the extension of interventions able to restore runway evenness. In this paper, the roughness assessment of real runway profiles is carried out using first of all BBI and IRI but also ProFAA simulation model, with particular attention to Cockpit Vertical Accelerations, underling the different impact on airport pavement management of the results provided by them. In particular, very low correlations for the whole sample of examined profiles were found between IRI and BBI (R2 = 0.11) and between IRI and cockpit vertical acceleration (R2 = 0.03), while a better correlation was obtained between BBI and cockpit vertical acceleration (R2 = 0.59). Neglecting runway profiles characterised by long wavelengths roughness, a very high correlation between IRI and BBI (R2 = 0.91) was found, that underlines their different sensitivity to long wavelengths. In particular, it was found that for roughness characterised by low wavelengths, the IRI method seems to be more conservative than BBI. In addition, two different IRI acceptance thresholds were taken into account, one used in South Africa (2 m/km) and one adopted in Canada (2.7 m/km). For the whole profiles sample, little differences were found in their runway sections evaluation (about 4%) compared to BBI method; while, considering the reduced sample where profiles characterised by long wavelengths roughness were excluded, the use of IRI limit of 2 m/km would seem to be too conservative.