Highways Agency - Safe roads, Reliable journeys, Informed travellers

Carriageway profile

6.1 An extremely detailed survey of the 600 metre section of the westbound carriageway of the M62 Motorway between Marker Posts 146/9 and 146/2 (i.e. the immediate approach to Little Heck Railway Bridge) was undertaken on 4 March 2001 using the Highways Agency Road Research Information System (HARRIS) survey vehicle.

6.2 Continuous measurements of the following parameters were made in the hard shoulder and the first running lane (Lane 1):

• Global Position and Curvature - to determine the carriageway alignment / straightness;
• Altitude - to determine the height of the carriageway above / below a set datum;
• Gradient - to determine the gradient of the carriageway;
• Crossfall - to determine the transverse fall of the carriageway;
• Sensor Measured Texture Depth - to determine the macrotexture of the carriageway surface;
• Variance - to determine the ride quality of the carriageway surface;
• Rutting - to determine the depth of any carriageway rutting.

6.3 The survey runs were repeated to ensure that the accuracy of the measurements was of a high standard.

6.4 The data obtained can be analysed at intervals of any multiple of 1m. However, for assessment of pavement condition on a Network level it is common for results to be aggregated into 100 metre lengths. This has been done with the data obtained from the M62 motorway, with the data being tabulated and included at the end of this section of this report.

6.5 The conclusions that can be reached from the HARRIS data obtained are as follows (with reference, as applicable, to threshold values and categories contained within technical standard HD 29/94, which can be found within Volume 7 of the DMRB):

• The variation in the measured parameters along the length of the 600 metre section can be shown to be no different from the variation that would be typically obtained along the length of a sound carriageway surface;
• There is no evidence of any extremes of longitudinal or transverse profile or unacceptable profile shape, when examined in comparison with profiles typically recorded on motorways and other trunk roads.
• With reference to the requirements of the DMRB it can be seen that acceptable levels of carriageway rutting and ride quality (variance) are obtained. The ride quality is considered likely to fall into the upper quartile of sites (if not better);
• There is no evidence of any extremes in carriageway rutting. Rutting in the nearside wheeltrack is of a greater magnitude than that found in the offside wheeltrack. This is not untypical of the rutting generally found on the English motorway and trunk road network. Rutting in Lane 1 increases as the site of the bridge is approached. This may be related to the slight incline in the carriageway at this point, as increased vehicular loading on inclines is a well known phenomenon that can lead to an increased propensity for rutting to develop in the wheeltracks. None of the rutting found at the site can be considered deep or unacceptable;
• Texture Depth has been commented on in Chapter 5 of this report;
• The crossfall of the carriageway is consistent with that generally found on straight UK Motorways and Trunk roads at 2 - 2.5%;
• There is a steady incline at the site with a gradient of approximately 1.5%. This level of incline can be considered slight, and is by no means high it terms of the inclines that can be experienced on UK Motorways and Trunk Roads;
• The curvature readings taken on the site show a radius exceeding 2000 metres, i.e. the site is effectively straight in alignment.

6.6 The HARRIS survey data from the Little Heck site are shown in Appendix 1 of this report.

6.7 In summary, the HARRIS data obtained shows that the westbound carriageway of the M62 Motorway between Marker Posts 146/9 and 146/2 exhibits no extremes in alignment, gradient, profile or rutting and is indicative of a sound carriageway surface.

Vibra-Line ("Rumble Strip") Provision

6.8 As stated in Chapter 3 of this report, the edge line marking between the hard shoulder and Lane 1 of the westbound carriageway at the material location consists of vibra-line, which is sometimes referred to as a "rumble strip", as it creates an audible warning to drivers when their vehicles leave the traffic lanes.

6.9 The requirements for road markings are given in Statutory Instrument No. 1519 "Traffic Signs Regulations &General Directions 1994", which came into force on 12 August 1994. This document specifies road markings by reference to various diagrams, with longitudinal edge markings shown in Diagram 1012.1.

6.10 Diagram 1012.2 shows an "alternative to the marking shown in diagram 1012.1 incorporating an audible and tactile warning in the form of a raised rib for use on motorways" and specifies the requirements for vibra-line/rumble strip.

6.11 Such markings consist of continuous white lines approximately 200 mm wide incorporating transverse ribs which are approximately 50 mm long and raised by 9 mm above the adjacent surface of the marking. The raised ribs are provided at intervals of approximately 500 mm.

6.12 The inspection and maintenance of road markings is carried out under the procedures described in the following Chapter of this report.