The Rolling Straight edge simulates a 3m rigid straight edge sliding along the road surface, and consists of a rigid frame supported on rubber-tyred wheels arranged in two parallel rows, with the centres of the wheels in one row opposite the gaps between the two parallel rows of supporting wheels, is free to move such that it detects vertical movements of this wheel which are then transmitted to a pointer and scale, on the instrument head.
The Rolling Straight edge was developed in conjunction with TRL. It is produced as an instrument to assist engineers with construction, quality control and with compliance assessment, of newly laid pavement regularity.

The Rolling Straight edge measures depressions on the pavement surface on analogue scale 0-12mm + 0.25mm. The straight edge also has an odometer for accurate determination of distance travelled in units of 1 metre.

The Rolling Straight edge is pushed at 1-2km/h and the number of irregularities, their length and distance from start, are recorded. The national specifications for surface regularity are then compared and the pavement accepted or rejected and or remedial work undertaken.

References

T.S.O. - Highways Agency - Specification for Highway Works. This document details requirement in term of the maximum permissible number of irregularities beneath a Rolling Straight edge.
TRL - Supplementary Report 290 - details the calibration, maintenance and use of the Rolling Straight edge.

Specification

The rolling straight edge is shipped in 3 wooden cases with a total gross weight of 112kg.

Dimensions

Case 1: 1110 x 520 x 400mm
Cases 2 & 3: 1240 x 380 x 410mm

Click to view a PDF file of the User Guide