Civil Engineering

Fast and accurate filter drain condition surveys to support targeted interventions.

SmartScan has been developed by Carnell as a ‘risk-based approach’ to the condition assessment of roadside filter drains. Using innovative data capture technology combined with bespoke reporting software, an accurate analysis of the filter drain asset’s performance is quickly produced.


> Maximum surveying speed of 20kph
> Reach of 3.5m from the carriageway edge
> Surveys both verge and central reservation
> Works under 12c TM (mobile lane closures)
> Can be used in all TM scenarios
> Integrated office facilities ensure accurate survey
> Welfare facilities


Filter drains service a large proportion of the strategic roads network and it is crucial that they are well maintained, to effectively remove water from the carriageway. The nature of their construction means that this asset has proven to be difficult to accurately assess.

Limited budgets mean that an unequivocal and efficient survey technique is required to identify and prioritise essential maintenance.


Carnell’s fleet of custom-built SmartScan vehicles undertake a high speed, non-intrusive investigation of the roadside filter drain’s surface and sub-surface condition. The survey is carried out in accordance with new highways drainage standard CS 551 Drainage surveys (Section 5: Filter drain condition survey by GPR).  Data is captured to CD 535 Drainage asset data and risk management specification ready for upload to HADDMS.

A lean tool to improve network knowledge by increasing the quality of drainage network condition data, it assists in the value management process and development of the forward programme.

comparison to traditional techniques


Increase in survey output.


of cost of walk over survey.


of filter drain assessed.

CS 551

& CD 535 compatible output, uploadable to HADDMS.

Detailed filter drain condition assessment

SmartScan is a cost-effective way of proactively identifyingat-risk areas along the highways network. This enables the prioritisation of remediation activity and the development of a targeted and long-term maintenance strategy.

1. Versatile Operations

Integrated LED 610 arrow board for use in 12C mobile lane closures for works in verge and central reserve on all road types.

2. Asset Assessment

Survey Technician captures detailed information including road camber, barrier location and embankment type, in the integrated mobile office.

3. SmartScan Condition

Accurate condition of filter drain captured by radar horn. Telescopic scanner with a reach of up to 3.5m from the carriageway edge.

CIHT Awards Judges

Winner: Technical Application

It has significant benefits for both industry and society by targeting maintenance interventions at identified locations, consequently reducing pavement deterioration and causing less disruption to the public.


The advantages of SmartScan support Highways England three imperatives:

  •  Quicker surveys reduce road worker exposure.
  • Informed interventions alleviate carriageway flooding.
  • Non-intrusive technique.
  • Mobile working eliminates TTM installation and removal.
Customer Service
  • Targeted approach means fewer interventions and lane closures.

  • Mobile works reduce network occupancy.

  • Improved assets means more comfortable journeys.

  • Stress free journeys through reduced flooding events.

  • Robust evidence for Value Management Process.

  • More efficient, risk-based inspection regime.

  • Improved knowledge of asset condition.

  • Half the cost of traditional filter drain condition assessment.

  • Better use of funds.


SmartScan was introduced to the Highways England market in 2012. Since then the process has been continuously improved, whilst keeping to the original ethos of providing unequivocal data on filter drain condition at exact locations.

In areas where historical SmartScan surveys took place, there is the opportunity to re-scan them and compare up to date condition against earlier data grades.
This information will allow a model to be developed identifying the ‘at risk’ areas and time frames for the end of life expectancy for the filter drain asset.

This approach will inform the development of a targeted maintenance program to maximise the effectiveness of available funding whilst supporting a robust Section 58 defence.


Since their initial construction, the effectiveness of filter drains will gradually reduce as silt and fines from surface run-off fills the voids between the aggregate. In places, an impermeable barrier will be created leading to standing water in the running lanes. Ignoring this problem would lead to road-user safety being compromised and a deterioration of carriageway
sub-base layers, reducing its life-span.


Whilst traditional techniques are subjective with intermittent detailed analysis, SmartScan provides a non-intrusive, evidence-based assessment of the entire filter drain length.

The survey detects the level of porosity within the filter material, indicating where the capability to transmit water from the surface or the adjacent pavement to the carrier pipe is restricted. Bespoke software then assigns a condition rating to a defined length of filter drain.

These condition shapefiles can be uploaded to HADDMS as well as Carnell’s DrainageViewer. This web-based GIS interface can be accessed by authorised users to identify which areas of filter drain are in the worst condition and where they coincide with flooding hot-spots.

Front and rear cameras capture “beginning to end” video evidence stored on watermarked hard drive.

Rapid Reporting

Location information, video footage and Dynamic asset display.

Detailed filter drain condition assessment.

Innovations that show the way


Mobile road worker protection system


Sustainable In-Situ Filter Drain Refurbishment


Carbon & Customer Considerate Compounds