The effect of road texture on road users and road maintenance

Paallysteiden pintakarkeuden vaikutukset tien kayttajiin ja tienpitoon

Texture of road pavement is defined according to the ISO-definition in to three different definitions (micro-, macro- and megatexture) which cover longitudinal wavelengths 0.001-0.5 mm, 0.5-50 mm, and 50-500 mm. In Finland texture data (macro and mega) of road pavements has been collected with high speed measurements together with rutting and IRI-measurements. The total amount of measurements is about 30 000 km per year. All measured variables have been calculated as RMS-values. Microtexture of a pavement is a useful feature because it improves the friction between tire and pavement. However it is not very significant in Finnish road pavements for two reasons; it is not possible to measure it with high speed monitors and the polishing of pavements is not recognised to be a problem with Finnish heavily rutting pavements. Macrotexture of a pavement has manyfold effects; it improves friction but increases rolling resistance. The short-wave macrotexture has an effect to decrease the rolling noise and is therefore a useful property but the long-wave macrotexture increases noise. It is recommended to split the macrotexture variable in to two parts according to a threshold wavelength value, 10 mm. Macrotexture of wavelengts 0.5-10 mm could be called fine macrotexture and macrotexture of wavelengths 10-50 mm could be called rough macrotexture. In many studies macrotexture has been measured either as RMS-value or MPD-value. RMS-value is not very sensitive to the vertical orientation or direction of the surface texture. Instead of RMS-value the MPD-value is sensitive to the vertical orientation and that is why the ratio of those variables can tell something valuable about the nature of texture. The orientation of surface with texture of MPD>RMS is called positive and with RMS>MPD called negative. New pavements in Finland usually have negative oriented texture. Negatively oriented pavements have several positive characteristics; they are nice to drive, low-noisy and they have a high friction level. Probably the rolling resistance on negatively oriented texture is lower than on positively oriented pavements. When the pavement gets older it loses the negative texture and it transfers to very strong positive texture and most of the good characteristics disappear. Therefore it would be useful to measure both variables RMS and MPD and focus on the orientation of texture as well. Megatexture of a pavement is short-wave unevenness which is coming from wavelengths between macrotrexture and roughness (IRI). Megatexture increases rolling resistance and tire and vehicle wear and is therefore an unwanted charasteristic of a pavement. The initial value of megatexture depends on the quality of the treatment and remains quite stable during the aging of the pavement. Some irregularities as potholes, slab joints, bridge expansion joints and so on are also increasing megatexture. Values above 1.0 are high values. Finnish pavements have been mostly made using the maximum aggregate size of 16 mm (77%). The most frequently used pavement types for high-volume roads are SMA 16 and AC 16. The pavement design for high-volume roads has been based strongly on the rutting problem, and less emphasis has been put to other features. In general the pavements are quite noisy and there has been made lots of research and development work to get less noisy pavements (especially in urban areas). The texture data of pavements has been mostly unused. This study is trying to lift up the meaning and potential of texture data. It seems that the texture as a whole have several different effects and should be taken into use in the area of pavement design. The most acute need is to start measuring the correct texture variables. That means that the variables must be derived from the physical mechanisms and effects of the phenomena. Macrotexture variable needs to be split into two parts and the texture orientation should be measured as well. More research is needed to find out how the texture is affecting to the three common outputs; rolling resistance, rolling noise and friction. More research is also needed to find out how pavement design and new variables relate to each other. After these goals it is possible to estimate the economic importance of the texture of pavements in more detail. International co-operation is also needed to transfer results from other national and international results into Finnish circumstances. This report may be found at http://alk.tiehallinto.fi/julkaisut/pdf3/lts_2010-01_paallysteiden_pintakarkeuden_web.pdf

Language

  • Finnish

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Filing Info

  • Accession Number: 01334359
  • Record Type: Publication
  • Source Agency: Finnish Transport Agency
  • ISBN: 978-952-255-001-9
  • Files: ITRD
  • Created Date: Mar 28 2011 2:35PM