A Deflectograph is a survey vehicle used to produce data for the assessment of pavement strength. It is a lorry-based system, with a pair of wheels at the front and a pair of double wheels at the rear. At the start of testing, a pair of deflection beams are lowered onto the road surface. The Deflectograph then moves forward, so that the double wheels on the rear of the vehicle straddle the two beams. This causes the pavement to deflect (due to the vehicle’s weight) which is measured in the two beams. Once the rear wheels have reached the end of the beams, the beams are brought forward and the process is repeated again. This results in deflection measurements taken at approximately 4m intervals. These machines survey at 2.5km/h and are further discussed in CS 229 (part of the Design Manual for Roads and Bridges or DMRB).

The Accreditation and QA requirements for these devices are given in the Accreditation and QA specification.


 If you are looking for a contractor to carry out Deflectograph surveys compliant with HD29 on your behalf, you may wish to check the list of Deflectograph Survey devices below. On this page, you can also find the latest accreditation certificates. In this table, machines are referred to as having met criteria if they have met the mandatory criteria as defined in the Accreditation and QA specification for these devices. Some Network Authorities may also require a specific level of performance in some or all of the additional tests. Please see the certificates for more detail on the performance of these devices in these additional tests.

ID Reg plate  Operating company Met criteria Certificate
02 L697 BKR PTS Yes 2023 DFG 02
03 B180 FBL TRL Yes 2023 DFG 03
05 D962 JRU WDM Ltd Yes 2023 DFG 05
08 BYW 80V WDM Ltd Yes 2023 DFG 08
09 VGV 182X WDM Ltd Yes 2023 DFG 09
10 F569 JBB WDM Ltd Yes 2023 DFG 10
12 EOU 230W WDM Ltd Yes 2023 DFG 12
14 B195 CFW Lincolnshire CC Yes 2023 DFG 14
15 ACZ 3268 DfI Northern Ireland Yes 2023 DFG 15
16 B880 XOU WDM Ltd Yes 2023 DFG 16


Sign up to the APM Newsletter.