Northern Ireland Road Network and Condition Statistics - Background Quality Report

Q3.3 The quality of the statistics and data, including their accuracy and reliability, coherence and comparability, and timeliness and punctuality, should be monitored and reported regularly.

Introduction

Context for the quality report.

The Department for Infrastructure (DfI, the Department) has responsibility for the road network in Northern Ireland. Under Article 8 of the Roads (Northern Ireland) Order 1993, the Department has a statutory duty to maintain the province’s road network. Analysis, Statistics and Research Branch (ASRB), a Northern Ireland Statistics and Research Agency (NISRA) branch within DfI produce and publish the ‘Northern Ireland Road Network and Condition Statistics’ report.

The statistical report published in 2023 is the first report in this statistical series. The report was produced and published following engagement with stakeholders and after a period of intense quality assurance of the methodology and outputs. The aim is to publish this report annually.

A user engagement exercise carried out on Northern Ireland Transport Statistics identified an interest in the statistics formerly produced within Chapter 1 of the Transport Statistics bulletin. Furthermore, a Northern Ireland Audit Office Report (Structural Maintenance of the Road Network), made a number of recommendations, one of which was the publication of robust road condition statistics and for the Department to enhance our user engagement. This was followed by a report by Jim Barton on the review of structural maintenance funding in 2018.   In addition, the volume of queries received on road conditions highlighted that there is a need to publish robust statistics on the road network in Northern Ireland.

The report, which includes user guidance, is published on the DfI website (add link).

Relevance

The degree to which the statistical product meets user needs in both coverage and content.

The Northern Ireland Road Network and Condition report is a new Official Statistics bulletin published to meet stakeholder needs. Statistics on road lengths and conditions are currently published by the Department for Transport, Transport Scotland and the Welsh Government.

The quality and reliability of a region’s transport networks are recognised as major factors influencing its competitiveness and potential for growth. Northern Ireland’s road network is of key economic and social importance. In the absence of significant rail freight in the region, all goods and services essentially travel along the road network alongside passenger transport. The report includes statistics on road length, road condition and expenditure on roads in Northern Ireland. The information is broken down by Local Government District where possible to meet the needs of both internal and external users.

The statistical product includes an html publication containing maps, charts, infographics and associated commentary. There are also detailed tables and a standalone infographic available to meet the needs of different users. The background to the publication, as well as key methodology and quality information are included within the publication. In addition, all data are provided in Open Document spreadsheets. A more detailed Technical Report is also available.

Accuracy and Reliability

The proximity between an estimate and the unknown true value.

The road length and condition data are supplied to ASRB by the Road Asset Maintenance branch within DfI Transport and Road Asset Management. In Northern Ireland, road condition is expressed in a broad number of ways and by a number of various survey techniques. The road condition statistics in the report are based on two key surveys: SCANNER (Surface Condition Assessment for the National Network of Roads) and  Deflectograph. Further detail on each of these surveys is provided in the Technical Report.

The SCANNER survey, which is both accredited and  under contract, is undertaken annually on the majority of road classes including: 100% of the Trunk Road Network (TRN) and A class network in one direction each year, with the opposite direction being surveyed the following year; and on 25% of the B & C Class network each survey year in both directions.

Deflectograph surveys are carried out by an accredited slow moving vehicle that measures the deflections of the roads surface under defined loading and uses this information to calculate the residual life of the road pavement and the need for structural repairs; essentially this survey assesses the structural integrity of a roads base and natural foundations.  Currently Deflectograph surveys are carried out on one third of Motorway, TRN and non-Trunk A roads each year in NI.

DfI Road Consultancy Services (Materials Engineering and Assessment Section, MEAS) carry out the Deflectograph survey. Once the data from this survey are collected by the survey teams on site, they are then processed in-house by the MEAS staff in the first instance; this is done via the WDM Pavement Management System (PMS) software (which only MEAS staff have access to).  This process, known as fitting, is carried out by trained MEAS staff and involves raw survey data taken directly from the machine being inputted into the PMS, with checks, and balances from calibrations and seasonal factors etc. taken into account. Once the raw data have been through the first stage of processing, WDM will handle all subsequent stages thereafter, due to protocols around data safety and system integrity.

Both road condition surveys methods follow agreed national specifications and guidelines and well established accreditation and quality assurance procedures are in place and documented. Further information is available on the UK Roads Liaison Group website.

Data on surface defects instructed and repaired are downloaded from the Road Maintenance Client System (RMCS). This is a live system which is continuously updated and data on defects treated are downloaded at a point in time. This system is also the source of information on road lengths in Northern Ireland. Quality Assurance of Administrative Data (QAAD)

The expenditure data are provided to ASRB by DfI Finance Business Partner and are extracted from Account NI after the end of the financial year. Account NI has various levels of control built into the system such as delegation limits and hierarchy authorisation.  These controls are in line with DfI’s Accounting Procedures manual and would be subject to Internal DfI Audit.  Further information on the quality of these data is also included in the Quality Assurance of Administrative Data (QAAD).

The QAAD quality assessment of the administrative data sources used to produce the road network and condition statistics found that the level of risk of quality concerns in these sources is low.

For all data received, variance/logic checks are employed by statisticians as an integral part of the production process with any large variances between current and previous years queried with the data provider to ensure these changes are accurate and can be explained e.g. improvements following a major road resurfacing project.  Previous data are revised if necessary and appropriate.  All revisions are conducted in line with ASRB’s Revisions and Errors Policy.

Timeliness and Punctuality

Timeliness refers to the time gap between publication and the reference period. Punctuality refers to the gap between planned and actual publication dates.

The data on road lengths are downloaded from the RMCS at 1 April each year.

The road condition survey data are reported against the financial year in which the surveys are undertaken. The SCANNER survey is usually carried out from approximately May to October each year. Once the data are downloaded from the survey vehicles and processed through the PMS, the updated results are input into RMCS and available to DfI Transport and Road Asset Management around November time.

The Deflectograph survey season runs from April to June (approximately) before taking a break of around two months before finishing in October. After the Deflectograph data are processed internally by MEAS and then by WDM, they are updated to the RMCS and available to the DfI Road Asset Maintenance team usually by the end of the following January.

Once all the survey data have been collated and checked by the Road Asset Maintenance team, they are provided to ASRB. It is hoped that in the future survey data can be supplied in a more timely way.

The expenditure on roads data are reported for the previous financial year. The financial data are usually provided in the summer to ASRB and once validation of the data is completed.

As the release at the beginning of December 2023 was the first report in this statistical series, there was a lag of just over eight months between the end of the financial year being reported on and the publication date. ASRB continue to work with DfI Transport and Road Asset Management to improve the timeliness of the report. The current aim is that the second edition of the report will be published in Autumn 2024.

Advance notice of ASRB publication dates is available in the upcoming statistical releases calendar on the DfI website.  Publication dates are also pre-announced on GOV.UK.  The first edition of this publication was released on time.  In the event of a change to a pre-announced release date, the delay would be announced and explained on both the DfI website and GOV.UK and the new publication date specified.  If necessary, updates would be given regularly.

Accessibility and Clarity

Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the metadata, illustrations and accompanying advice.

The report is published in html and is available free of charge on the DfI website.

The statistical tables are also available to download in MS Excel format and ODS (Open Document Spreadsheet) format, from the webpage.  Relevant tables are also being made available on the NISRA data portal following publication of the report; these data can be exported to CSV (Comma Separated values) and other formats.

The publication is accessible through the UK Official and National Statistics Publication Hub.

User Information is included in the publication to help users to understand and make the best possible use of the data.  Maps have been embedded into the publication so users are clear on the road network coverage.  In addition, where necessary, explanatory footnotes are included in the tables.

Every effort has been made to comply with the AA standard under the WAVE Web Accessibility Evaluation Tool (webaim.org)(external link opens in a new window / tab).

The publication contains contact details of the responsible statistician who can be contacted for further information.

Coherence and Comparability

Coherence is the degree to which data that are derived from different sources or methods, but refer to the same topic, are similar.  Comparability is the degree to which data can be compared over time and domain.

Statistics on road lengths and conditions are currently published by the Department for Transport, Transport Scotland and the Welsh Government. A range of survey data are reported for England, Scotland and Wales but users should note that the responsibility for road maintenance sits with various bodies in GB while in NI, DfI has responsibility for the entire road network.

Data on road lengths are derived from the same source over time and are comparable between years.

The data on road conditions come from a range of sources and each source measures a different aspect of road conditions. The data from the various data sources cannot be compared but comparisons can be made over time within each individual source. As part of the engineering analysis and statistical quality assurance processes, the latest data are compared with the previous years’ data where appropriate. This allows for an assessment of trends in the condition of the various road networks across Northern Ireland, while providing local engineers with the most up to date data in order to allow better decision making on interventions and funding allocations.

The data on expenditure are derived from the same source over time and are comparable between years.

Trade-offs between Output Quality Components

Trade-offs are the extent to which different aspects of quality are balanced against each other.

There are not considered to be any trade-offs.

Assessment of User Needs and Perceptions

The processes for finding out about users and uses, and their views on the statistical products.

In line with the ASRB User Engagement Strategy, the content of the publication is informed by an understanding of customers’ information needs. The data presented in the publication aims to meet the needs of both internal and external users. A user engagement exercise carried out on Northern Ireland Transport Statistics identified an interest in the statistics formerly produced within Chapter 1 of the Transport Statistics bulletin. This survey, along with stakeholder engagement, informed the first publication of NI Road Network and Conditions. All users on the Transport Statistics distribution list were notified of the development of a new Road Network and Condition report and asked to opt-in to the new distribution list if interested in this topic.

In the NIAO Structural Maintenance of the Road Network report, the Northern Ireland Audit Office recommended that the Department should publish information regarding the condition of the road network on a regular basis. The report also referred to the need for the Department to communicate, consult and engage with all stakeholders regarding the condition of the road network. This statistical report and the associated user engagement will support the Department in meeting these recommendations. 

SCRIM (Sideways Coefficient Routine Investigation Machine) surveys measure the skidding resistance of road surfaces. Currently SCRIM surveys are carried out annually on the Motorway and TRN and on one third of the non-trunk A Class road network. At present, SCRIM data are fit for operational purposes but are not yet deemed to be sufficiently robust for statistical reporting but ASRB will continue to liaise with DfI Transport and Road Asset Management to determine if these data can be published in the future.

The volume of queries received from local councillors and community groups on road conditions, along with the public and media interest in this topic, highlighted that there is a need to publish robust statistics on the road network in Northern Ireland.

There is an ongoing ASRB customer satisfaction survey, which includes a question on whether ASRB publications meet customers’ needs. The link to the survey is issued every time users are notified that a report has been published or when an ad-hoc query is answered. Results are collated on a quarterly basis.

Following the first publication of the Road Network and Condition Report, users will be consulted to determine if the published report meets their needs.

Performance, Cost and Respondent Burden

The effectiveness, efficiency and economy of the statistical output.

In the production of this publication, ASRB endeavour to operate efficiently by placing the minimum load necessary on data providers. The only cost to the data providers is their time involved in extracting/transferring data and any follow up queries. Data providers are content to bear this cost given the benefits of publishing the statistics and the need for open and transparent data.

ASRB has worked closely with the Road Asset Maintenance team and the DfI Business Partner to agree the most effective and efficient way to format and transfer data. There is ongoing communication with data providers to ensure the timely receipt of data.

On receipt of the information, statisticians validate data and prepare for publication.

This may involve further liaison with data providers. Once data are verified, statisticians prepare for publication within a short timeframe.

Confidentiality, Transparency and Security

The procedures and policy used to ensure sound confidentiality, security and transparent practices.

ASRB adhere to the UK Statistics Authority (UKSA) Code of Practice for Statistics in the dissemination of the Road Network and Condition Report and our statistical practice is regulated by the Office for Statistics Regulation.

The data are transferred via DfI’s secure record management system (Content Manager), and are subsequently stored on a secure and accredited network drive that is only accessible to relevant ASRB staff. Personal information is not collected and statistical disclosure control methods do not need to be applied to the data.

ASRB’s Data Governance and Confidentiality Statement is available on the DfI website.

Further Information

For further information relating to the quality of ‘Northern Ireland Road Network and Condition Statistics’, please contact ASRB@nisra.gov.uk

Last updated: December 2023