Annex 1 - Carriageways (Road Surface)

Contents

1. Introduction

Delivery of a safe and well-maintained highway network relies on good evidence and sound engineering judgment. Asset management is widely accepted as a means to deliver a more efficient and effective approach to management of highway infrastructure assets through longer term planning and ensuring that levels of service are defined and achievable within the resources available.

It is accepted that transport infrastructure is absolutely critical to the wellbeing and economy of the County and the wider UK and therefore the condition of the carriageway is of great importance. The National Highway Transport (NHT) surveys show consistently that carriageway condition and road safety are the most important highway services with condition being considered the most in need of improvement. If the Council is to support economic growth, and the health and wellbeing of the travelling public in Devon, it is essential that the Council ensures its highway infrastructure is fit for purpose.

Devon has the largest road network of any Local Highway Authority in England with a total of 13,000 km of road consisting of 8% A roads, 5% B, 35%C and 52% unclassified. Only 2,916 km of road are classified as urban with the remainder serving local communities within rural environments. In addition, the network is affected heavily by seasonal variations in traffic volumes with flows on roads of all types increasing significantly during the peak summer months. This contributes to congestion issues, particularly on our principal routes, and increases carriageway deterioration on our minor roads during these periods.

The construction of Devon’s road network is diverse ranging from designed roads constructed to modern standards to those which have evolved over many years having originated from historic tracks whose construction is often limited to various layers of surface dressing and patching. This presents significant challenge when managing the asset and maintaining the network in a safe and useable condition.

In keeping with the recommendations of the CoP the core approach adopts a risk approach for all aspects of its highway infrastructure maintenance.

2. Inventory and Hierarchy

2.1 Inventory

A detailed highway inventory is an essential prerequisite of establishing a cost effective and adequate maintenance regime.

The inventory is the foundation on which asset management is built and when analysed in combination with other information sources, for example, condition data, road casualty reports and traffic flows. It is also used in combination with intelligence gathered from stakeholders and experts to determine priorities. All of this provides crucial decision supporting information.

Inventory Set	Inventory Item
Carriageway (Road Surface)	Central Reserve
	Central Island
	Lay-by
	Roundabout
	Kerbs
	Channels
	Level Crossing
	Cattle Grid
	Gully
	Catchpit / Interceptor
	Inspection Cover

Fig. 1.1: Highlighting various inventory items that are associated with the carriageway. Some of these items are also associated with drainage and will appear in further annexes.

2.2 Network Hierarchy

The development of a carriageway maintenance hierarchy is the foundation of a coherent consistent and auditable asset inventory as it provides the organisation structure to the inventory.

The hierarchy reflects the needs, priorities and actual use of each road and will be used as a tool in determining priorities maintenance standards, targets and performance.

The current hierarchy is detailed below and also highlights the various lengths of carriageway associated with each level.

Carriageway Maintenance Category	Hierarchy Description	Type of Road / General Description	Length of Category in Devon (KM)	Percentage of Network
1	Motorway	Maintained by National Highways	N/A	N/A
2a	Primary National – Trunk Road	Maintained by National Highways	N/A	N/A
3	National Primary route	National strategic routes for through and long distance travel (A roads)	373.4	2.9%
4	County Primary route	Main access routes connecting principal settlements.	473.8	3.6%
5	Secondary County route	Main access routes to large settlements and recreational attractions.	801.8	6.2%
6	Local Distributor	Main access routes to smaller settlements and recreational attractions.	1250.3	9.6%
7	Collector road	Rural – Access routes to small villages and other significant traffic generators. Urban – Industrial main collector roads & through routes and Residential collector roads. Access to schools, hospitals, facilities for the disabled, main shopping areas, libraries, car parks and tourist attractions. Shared surfaces with heavy pedestrian traffic. Local roads serving limited numbers of properties.	1548.7	11.9%
8	Minor Collector road	Rural – Roads serving small hamlets and scattered communities. Urban – Roads serving shopping areas, business premises, industrial estates and residential areas	2072.5	15.9%
9	Service road	Rural – Local road serving only a few properties Urban – Narrow collector roads and shared surfaces	5047.7	38.8%
10	Minor Service road	Rural – Local road serving only one property Urban – Cul-de-sac serving less than 20 properties.	691.8	5.3%
11	Minor lane	Rural – Serving fields only or duplicating other routes. Urban – Back Lanes	152.3	1.2%
12		Not used by normal vehicular traffic (Predominantly managed as part of Public Right of Way network)	589	4.5%

Fig. 1.2: Indicating the hierarchy of road types with a general description.

A review is underway to ensure the descriptors for each category accurately reflects the type of carriageway it represents.

3. Performance

3.1 Safety Inspections

Safety inspections are undertaken to meet the key objective of Network Safety and they form a key aspect of the authority’s strategy for managing liabilities and risks. They are used to identify defects likely to be hazardous or cause serious inconvenience to users of the highway network or the communities served, including defects requiring urgent attention and the appropriate response is determined using a risk-based approach.

The Highway Safety Policy details how safety inspections are undertaken, the frequency of inspection, investigatory criteria and required response period to an actionable defect. Relevant defects, treatments and Response Times are listed in the Highway Safety Policy.

3.2 Detailed Inspection, Network Assessment and Work Programme Identification

The network is regularly inspected by experts to identify and prioritise future works programmes. These inspections can take various forms but all are designed to collect visual data relating to the condition of the highway network so that works programmes can be formed and prioritised. Some of these inspections focus on detailed, specific elements of the highway inventory and can require specialist knowledge. Others can be more general looking at the condition of the asset along a particular route or an area.

3.3 Condition Surveys

The purpose of Condition Assessment is to address the key objective of Network Sustainability and to ensure that value for money is achieved when undertaking structural repairs.

By following asset management principles and providing information on the nature and severity of the condition, the timing and nature of appropriate treatments can be determined. Data from these surveys is also used in the production of National Indicators and repeatable condition surveys allow for analysis of trends within the network.

There are a number of different types of survey, each providing information from a differing perspective, and which in combination can provide a comprehensive picture of the condition of the asset.

Condition Surveys involve a diverse range of surveying and investigatory tools and equipment. A general overview of these surveys, along with links to more detailed descriptions can be found below.

SCANNER, (Surface Condition Assessment of the National Network of Roads) survey

This and MRM (Multi-functional Road Monitoring System), are machine-based surveys undertaken at normal road speeds that measures a range of road condition parameters using video and laser technologies. The vehicles are able to record a range of surface conditions including:

Longitudinal and transverse profile,
Surface Cracking,
Rutting and depth,
Texture depth,
Gradient,
Crossfall, and
Curve radius.

All of this information is processed into a pavement management system (UKPMS) which is used by engineers to help assess condition and determine maintenance requirements. The data is also used to calculate road condition performance indicators and assess asset value.

These surveys are used on a majority of the highway network at given intervals, with higher class roads being visited annually by SCANNER.

Fig. 1.3: SCANNER from WDM Ltd

Devon’s current survey contractor is WDM Limited, more in depth information can be obtained from visiting their website at wdm.co.uk SCANNER surveys

Deflectograph survey

These surveys are done through a Deflectograph machine which measures the deflection of the road surface under a load, which effectively determines the ‘strength’ of the carriageway. The data is no longer used as a national performance indicator for the Principal road network but can provide supplementary data for specific schemes requiring structural maintenance. With additional information about the road construction and traffic loading, the data can be used to determine residual life, design resurfacing treatments and understand future maintenance requirements.

Fig. 1.4: Deflectograph unit from WDM Ltd

Devon’s current survey contractor is WDM Limited, more in depth information can be obtained from visiting their website at wdm.co.uk Deflectograph surveys

SCRIM, (Sideways force Coefficient Routine Investigation Machine) survey

This survey measures wet road skidding resistance, which can then be compared to investigatory levels. It should be noted that there is no value at which a surface passes from being safe to unsafe; however, some sites due to geometric or other constraints often require higher levels of skidding resistance to reduce accident risks. This data is a prime factor in determining maintenance requirements on the Principal Road Network to ensure safety is maintained.

Fig. 1.5: SCRIM unit from WDM Ltd

Devon’s current survey contractor is WDM Limited, more in depth information can be obtained from visiting their website at wdm.co.uk SCRIM surveys

Visual Serviceability Inspections

Recent changes in programme development to the Local Asset Capital Programme has also developed an emerging practice of local teams undertaking driven inspections within the Parishes, to give a visual score of the asset/route condition. This information is recorded in WDM and used in conjunction with detailed data from condition surveys and information collaboratively gained from Parish/Town councils to inform programme development.

The score given and map information is seen in the example below:

Fig. 1.6: Visual Serviceability Scoring

Fig. 1.7: Example of Visual Serviceability Inspection Plan Overlay

Reporting by the public

A valuable source of condition data is the information the Council gather from the public when safety defects are reported. The provision of location of defects enables the contractor to optimise gangs in organising repairs in an efficient manner. With thousands of potholes repaired each month the data can be manipulated to identify carriageway sections that have high numbers of potholes.

Problems can be reported on the Council’s website which can be found on the Report a Problem page.

This condition data is used together with machine-based condition surveys to identify potential treatment sites.

3.4 Current Performance

Condition surveys are primarily intended to identify deficiencies in the highway infrastructure which if untreated are likely to adversely affect the long-term performance and serviceability of the asset. They provide information on the nature and severity of deterioration which is used to determine appropriate maintenance treatments and inform the asset valuation process. These surveys are used to provide assessments of overall performance, maintenance requirements and relevant data for national performance indicators.

SCANNER survey data is processed through a UKPMS and scores are given to every 10m section of road depending on the amount of defect found and assembled into a Road Condition Index (RCI). The RCI scores are then broken down into three categories, RED – requiring planned maintenance soon, AMBER – likely to require investigation soon, Green – generally good condition.

More detailed information on technical survey data and the scoring systems can be found in the Department for Transports Technical Note: Road Condition and Maintenance Data.

Road Condition

Carriageway condition is reported nationally using Road Condition indices generated from machine survey data processed using an accredited United Kingdom Pavement Management System. The results of survey analysis are presented below:

A roads

Fig. 1.8: Indicating the road condition specifically for A class roads from 2010/11 – 2022/23

B roads

Fig. 1.9: Indicating the road condition specifically for B class roads from 2010/11 – 2022/23

C roads

Fig. 1.10: Indicating the road condition specifically for C class roads from 2010/11 – 2022/23

Unclassified roads

Fig. 1.11: Indicating the road condition specifically for unclassified roads from 2010/11 – 2022/23

The DfT Technical Note: Road Condition and Maintenance Data provides definitions for the RCI categories and are as follows:

Green – ‘Good enough’ – No need to plan maintenance
Amber – ‘Continued deterioration’ – Needs investigating soon
Red – ‘Really quite bad’ – Planned maintenance soon

The current RCI condition shows that in periods of better funding, the Council has been able to make significant reductions in the amount of RED category condition carriageway, particularly on the minor, unclassified network. In recent years where funding has been more restrictive, the Council has managed to maintain condition in the higher class, strategic roads however, there has been a decline in the unclassified network.

Whilst this is useful to understand the condition of the carriageway, Devon County Councils response to these categories would be more in line with the Maintenance Service Standards detail in section 4.5. As such, the Council is likely to target treatment in the amber categories where efficiencies can be gained in selecting lower cost treatments to prolong the life of the carriageway. By taking this asset management approach the Council stands the best chance of reducing the amount of carriageway that becomes Red in the coming years.

With the current levels of funding the Council currently has the following targets in terms of carriageway RCI condition.

Asset Group	Asset components	Performance Outcomes
A roads	Carriageway condition	Limit RCI RED category to 4%
B roads	Carriageway condition	Limit RCI RED category to 4%
C and Unclassified roads	Carriageway condition	Manage and limit increase in RED category condition by targeting Amber Category for cost effective maintenance. RED category managed for safety.

Fig. 1.12: Indicating maintenance targets and outcomes set by the council.

4. Maintenance Strategy

4.1 Creation of a new asset

Devon’s carriageway asset is ever changing with predominant annual increases. New assets are created in a variety of ways, including:

Council schemes to create new roads which are funded through capital investment. These generally consist of bypasses, major link roads and relief roads,
Developer funded schemes can and do provide new carriageway particularly in the form of new housing and industrial estate roads. These are often adopted by the council once stringent conditions and specifications are met, and
Regeneration and improvements schemes are another source which can result in additional carriageway being created through widening.

4.2 Routine and Reactive Management

The council undertakes a range of cyclical highway maintenance activities which have the purpose of keeping the carriageway in good condition by allowing water to drain effectively, thus maximising the design life, these activities include but are not limited to:

Gully Cleaning,
Ploughing (Edge Cleaning),
Sweeping
Ditching

Over the years, some of these activities have been reduced in frequency, due to financial pressure. Some activities, such as programmed weed spraying, have ceased altogether. Where there is an appetite some local parish and town councils have taken on some of these tasks as part of the Council-led self-help schemes. However, with the prospect of further restricted funding, the ability to undertake these activities will be further impacted. This in turn will see a reduced ability to deal with water on the carriageway, which is leading to accelerated deterioration, earlier intervention of defect repairs and a reduced lifespan of the asset.

The Council’s highway inspection regime ensures that all the county’s roads are inspected at various frequencies dependent upon their category within the maintenance hierarchy and in accordance with the authority’s Highway Safety Policy.

Works identified as a result of inspections are assessed against certain criteria such as, carriageway category, size, probability of interaction with highway user and potential severity to determine how they will be treated, all of which is described in the Highway Safety Policy. Such treatment could include immediate temporary or permanent repair, scheduled treatment based on level of posed risk, or even inclusion in a future works programme. These reactive repairs are carried out to ensure safety of the highway user but also, to prolong the life of the asset where possible.

Alongside safety repairs, inspections will also highlight serviceability issues that may need resolving in the short term in an effort to prevent a safety issue and to maintain the integrity of the asset where possible. Where budget allows the authority may employ 2 forms of routine carriageway maintenance in this way.

Dragon Patching – a single vehicle and quick operation that uses flame to remove water and clean defects, followed by aggregate and binder sprayed into the affected area at high pressure to create the necessary compaction. These machines can treat numerous minor defects over a single day, and Fig. 1.13: Dragon patcher in operation
Serviceability patching – a more traditional form of patching. Small teams using hand tools can patch small areas of defective carriageway up to 50m2. These areas could be added to preventative programmes of work at a later date.

4.3 Renewal or replacement

With effective forward works planning and prioritisation, the Council aims to carry out both proactive treatments and major renewal or replacement at the right time for the right cost, ensuring the Council gets the maximum benefit for the cost.

Below are some examples of the type of treatment the Council make use of. The way these treatments are selected is indicated in section 4.6 below.

Types of Treatment

Recycling (Renewal/Replacement)  

There are three main types of recycling used for highway maintenance: 

Ex-situ – Ex-situ recycled material comprises bound material suitable for the construction of pavement layers produced in a fixed or mobile mixing plant from graded aggregate processed from arisings from the excavation of roads, blended, where necessary, with other aggregate and additives and bound with bituminous binder and/or hydraulic binder material. These recycled materials are typically used to replace traditional binder and base course layers.  The treatment is then followed with a surface treatment of either asphalt or surface dressing, 
Deep In-situ – The purpose of deep in-situ recycling, in conjunction with a new asphalt surface, is to strengthen the existing pavement by in-situ recycling using bitumen or hydraulic material as a binder.  This is achieved by pulverizing the pavement, which may be asphalt, hydraulic bound mixture or unbound material and binding the pulverized layer together with bitumen emulsion, foamed bitumen or hydraulic material. Materials are recycled to depths of between 150 mm and 450 mm and then followed with an asphalt overlay, and  
Shallow In-situ – The purpose of shallow in-situ recycling is to improve and regrade the surface of the existing pavement by pulverizing to depths between 75 and 150mm and then binding this material using bitumen emulsion, foamed bitumen, or hydraulic material.

Following the recycling process the surface is sealed using a surface dressing. 

Reconstruction (Replacement)

This treatment involves the removal of the existing pavement layers to remediate structural failure of the carriageway.  The depth of reconstruction is determined by the traffic flows, maintenance category and ground conditions, typically it will include the following layers:  

Base – Asphalt concrete dense bituminous macadam, 
Binder course – Asphalt concrete dense bituminous macadam, and 
Surface course – Asphalt concrete, SMA or HRA.

Where necessary the foundation layer will be replaced with a suitable depth of granular sub-base; and the correct design will give the structure of a carriageway a design life of 40 years, where the correct surface interventions are carried out during this time. 

Resurfacing (Replacement)

This treatment involves the introduction of a new asphalt surface, typically 40mm deep, to the road or footway.  This is achieved by either removal of the time expired existing surface or by overlaying the existing surface where it is of sound condition and surrounding thresholds allow.  Where current condition requires a binder course maybe included at a depth of 60mm either as isolated patching or across the whole scheme. 
Resurfacing provides a new running surface restoring skid resistance, surface profile and prevents the ingress of water to the lower pavement layers.

Surface dressing (Preventative)

This is a surface treatment that consists of spraying a film of binder onto the existing road surface followed by the application of a layer of aggregate chippings.  The chippings are then rolled to promote contact with the binder and to initiate the embedment in the underlying road surface. 
Surface dressing is a cost-effective way of restoring the road surface and sealing it against the ingress of air and water.

Lock chip (Preventative)

In essence this is the same as surface dressing however, there is an addition of a bitumen-based coating over the dressing once the dressing has achieved some embedment.
Due to the additional visits and processes this makes the treatment more expensive than normal Surface Dressing.

Micro Asphalt (Preventative)

This is a surface treatment applied by machine in two layers to the existing road surface comprising of aggregates up to 6/10mm bound with bitumen emulsion and hydraulic binders.  The treatment arrests deterioration by sealing surface from the ingress of air and water and by dealing with minor surface defects.

Hand Applied Slurry Surfacing (Preventative)

This is a surface treatment applied by hand in two layers to the existing carriageway surface comprising of aggregates up to 6mm, bound with bitumen emulsion.  The treatment arrests deterioration by sealing surface from the ingress of air and water and by dealing with minor surface defects.

Asphalt Preservation (Preventative)

This treatment for existing asphalt surfaces involves the spray application of a sealant treatment onto the road surface that consequently restricts water ingress and inhibits binder oxidation by providing a protective seal. 
This is a preventative treatment that is applied prior to deterioration of the existing asphalt surface.

Joint & Crack Repair (Preventative)

This treatment option deals with open joints and cracks in the existing carriageway up to a width of 150mm.  The area is filled using either a hot applied or resin system, the treatment seals the joint or crack to prevent the ingress of air and water and restores the surface profile.

Innovation

The Technical Appraisal Panel (TAP) assesses and trials new innovations in highway maintenance and repair, including carriageways. The main focus of the group is to address corporate aims, such as carbon reduction by establishing and approving a wider selection of treatments that can be used on the carriageway at various stages of the lifecycle. This may also bring about cost benefits compared to traditional forms of maintenance.

Site Selection

To inform the decision to ensure the correct design is selected for carriageway schemes the sites are investigated with the potential for core sampling along the scheme extents. Core samples are used to identify the current depth and condition of the existing pavement layers, also they are screened for the presence of coal tar. Where coal tar is identified, the core is fully analysed to determine whether the level is above the trigger point to classify the potential asphalt arisings as hazardous. The cost for the disposal of hazardous road arisings is prohibitive so the approach taken is to either design the scheme to negate the need to remove the hazardous material or where this is not possible the hazardous material is encapsulated using a recycling process.

4.4 Decommissioning of the asset

It is rare for carriageway assets to be decommissioned. This usually only occurs when roads are closed (or ‘stopped up’) because of major highway improvements or realignments. As a result of this, it is possible that sections of highway may fall into disuse or returned to the landowner of the subsoil beneath the highway.

The importance of maintaining an up-to-date asset inventory is recognised, taking into account the changes which do occur through planned activities and one-off events.

4.5 Maintenance Service Standards

Maintenance Service Standards were developed which define the Council provision for each asset type based on three levels:

Safety,
Safety and Serviceability or
Safety, Serviceability and Sustainability.

These terms are defined further in Section 3.3 of the lead section of this document.

These are defined in simple terms of what a road user could expect to see. This is very useful understanding the level of service in context of what is affordable.

Fig. 1.14: Indicating safety related issues and a description of typical appearance.

As pressures on budgets continue and become more restrictive, the ability of the Council to provide a service above that of safety is going to be severely impacted. This is illustrated in the tables below. Figure 1.15 illustrates the maintenance standards that can be expected on carriageways with current funding levels.

Fig. 1.15: Maintenance standards expected on carriageways

4.6 Treatment Selection

In conjunction with the maintenance service standards, the Council has also produced a treatment matrix which acts as a guide to the most appropriate materials/treatments to be used on the various categories of carriageway.

A link to the matrix can be found in Appendix 1 – 1.

The matrix uses a colour coding system to indicate the approved treatments for each category:

Green = Approved treatment,
Amber = Can be used with approval from Asset team, and
Red = Not to be considered on category of carriageway.

This matrix also gives an indication as to the carbon impact of each treatment, which will be important in the decision making process as the Council moves forward with the Carbon reduction strategy. As more becomes known about carbon cost through the carbon calculators, this element of the matrix will be updated. It is also important to note that Warm Mix Asphalt is given as the default material, which should only be changed following approval from the service manager.

As new treatments and processes become available, following approval by TAP, this matrix can be further updated.

5. Levels of Service and Investment Strategy

Levels of Service demonstrate the relationship between the Council’s corporate objectives, including the Strategic Plan for 2021 – 2025, and the performance of highway assets in terms of stakeholder requirements. The Levels of Service represent the fundamental service aimed at helping to deliver a road network which is as safe, reliable and as fit for purpose as possible within the current funding and resource constraints. Table 5.1 is an extract from the Strategy and shows the Levels of Service measures for carriageway surface along with an indication of how they relate to the Council’s Levels of Service Statements.

Measure	Responding to the climate emergency	Be ambitious for children and young people	Support sustainable economic recovery	Tackle poverty and inequality	Improve health and wellbeing	Help communities to be safe, connected and resilient
Continue the development of the Community Road Warden Scheme (CRWS) by providing training, equipment and materials to local volunteers to assist with carrying out minor amenity maintenance activities and repairing non-safety defects.	√		√			√
Respond within 2 hours to any occurrence or incident that poses a threat to life or renders the highway unusable or unsafe.			√	√		√
Using road condition data and community feedback to develop and deliver an annual programme of carriageway structural maintenance repairs including resurfacing, patching and surface dressing to maintain roads within available budgets.	√		√	√	√	√
Survey skidding resistance on A roads and investigate, monitor and repair deficiencies and/or put-up slippery road warning signs.			√			√
Operate a winter service of precautionary salting and snow clearance on strategic roads and when possible, on secondary routes as laid out in our Winter Service and Emergency Plan.			√			√
Support communities in their efforts to organise volunteers to clear snow and spread grit on routes considered locally important by providing support and training to snow wardens as well as equipment and bagged salt where applicable.			√			√

Fig. 1.16: Levels of Service

5.1 Lifecycle Model

An essential element of lifecycle planning is predicting the rate at which any given asset will be consumed. A deterioration profile can be developed from a variety of sources including historical performance, local knowledge and best practice. There is a complex deterioration model in use for carriageway condition.

Carriageways are a depreciating asset and constantly deteriorate. The primary factors in deterioration are the age of the carriageway, weather (particularly winter weather conditions) and traffic, particularly heavy goods. The cost of repairing that annual deterioration is known as Standstill or Steady State. Modelling of the carriageway component of the asset undertaken in 2020 indicated a need for approximately £50.6 million per annum to maintain carriageways in a steady state. The carriageway deterioration model has been developed with the Highway systems provider and is used to predict the future condition of the carriageway under a range of different funding and treatment scenarios.

The model has been developed to treat carriageways categorised as red and amber, as per Road Condition Index to model a typical treatment strategy which addresses both interventions on the worst sites, but also a preventative approach to intervene at a time before roads becoming more expensive to treat.

The model also calculates backlog (the cost of repairing all the RED sections of road network). Devon’s carriageway backlog was previously calculated as £167 million, however this is currently being revised to better reflect delivery costs, especially in light of inflationary pressures.

5.2 Investment Strategy

The current performance of carriageway assets, detailed in Section 4.0, show that Devon’s A, B and C roads are being maintained in a relatively steady state and good condition.

Unclassified roads combined with C roads, make up 87% of Devon’s Road network. The performance summary shows that the unclassified network has a relatively high proportion in Red and Amber categories, that should be considered for maintenance work immediately. This reflects the fact that the level of available capital funding is insufficient to carry out structural maintenance on the entire road network of the Council.

The current budget does not provide sufficient funding to meet the annual cost of deterioration of the asset and consequently the condition of certain elements of the highway asset will get worse. The Council’s strategy in this area will be to manage and mitigate that decline.

Whilst the funding prioritises the strategic routes, the authority’s asset strategy has a wider remit in ensuring all communities have access to a road infrastructure which allows communities to ‘Grow Up, Live Well, and Prosper’. It is necessary that the investment in the main roads is complimented by ensuring that good access to local communities is maintained. Therefore, an investment will continue to be made on roads outside of the A and B network that are included in the primary salting network, and other roads prioritised by several factors including:

Asset need identified by data,
Local information gained from communication with Town’s and Parishes, and
Expert knowledge from colleagues who understand the challenges of the local network.

This will help communities to feel Safe, Connected and Resilient in line with Best Place priorities.

Annually the Asset Management Team produce a Capital programme report for Cabinet which reviews progress on the current year’s schemes and the next year’s budget. The HSM Capital Budget and HSM Revenue Budget reports to Cabinet each year are built on and reaffirm the investment strategy for carriageways.

6. Programme Development

Devon Highways prepares an annual structured and prioritised forward works programme based on the investment strategy and available funding. Planning is important to operating a successful delivery programme, to aid efficiency, avoid abortive work and reduce disruption on the network. It is desirable that HSM structural schemes are designed at least one year prior to delivery. 

The in-year delivery programme still requires agility and flexibility and will change due to events (e.g. responding to weather events or the discovery of conflicts with other planned utility works, budgets). Schemes can be brought forward or deferred as required to help balance the programme in-year.

Fig. 1.17: Indicates the prioritised and forward works programme model

6.1 Identifying Schemes for an Initial Works Programme

SCRIM Sites

Devon limits routine annual SCRIM surveys to the principal road network only as it is considered neither affordable nor practicable for all roads on the highway network to be surveyed for skid resistance. The remaining untested network is covered under the strategy in the Annual Wet and Dry Collision Review, other roads identified as requiring further investigation are also be included in the programme of assessment.

It is not possible to treat all parts of the principal road network that are currently below the current standard therefore the work is prioritised and limited to potentially high-risk sites with a history of collisions. This includes sites with a reported skidding resistance deficiency and a history of collisions on wet surfaces, others with a high deficiency (greater than or equal to 0.15) and collisions on dry surfaces.

Principal Roads

There are a number of principal roads in the County that carry high vehicle flows and are of significant importance to the County’s economic prosperity. These include the A361, A39 west of Barnstaple, A380 and the main commuter and LGV routes to Exeter.

When undertaking maintenance of these roads a structured planned approach based on lifecycle planning should be adopted based on the known date of last maintenance treatment. Scheme timing will be verified by machine survey data and on-site evaluation. It is anticipated that preventative maintenance treatments will need minimal preparatory work. Prior to 2012/13 formal maintenance history was not well maintained; however, since then the Asset Team has endeavoured to capture relevant information. Approximate dates of previous maintenance works may be known to staff and where possible this should be considered in overall programming.

Maintenance schemes for these roads should be planned and designed well in advance and wherever possible be of a suitable scale. This scale is likely to be impacted by reducing budgets.

The remainder of the principal road network will have schemes developed primarily on the basis of machine survey and defect data combined with lifecycle planning. In addition to that, information gained from local teams around priorities and additional works will be taken into consideration. The aspiration is to produce schemes that address the site as a whole to reduce the need for multiple visits and increased disruption.

An issue in the identification of structural schemes has been the failure to appropriately identify and prioritise treatment of surface course failures where the defects arising do not trigger reactive safety repairs. Use of the Scottish MCIR (Maintenance Carriageway Indicator Resurfacing) has been promising and is being used to identify future works.

There is a need for reactive programming of failures either structural or surface which may be established through either survey or local report. Whilst these frequently do not generate safety defects, areas of delaminating surface compromise ride quality and can have a major impact on 2 wheel users. Surfacing schemes will be developed using a combination of MCIR indicator, reports of neighbourhood teams verified by site inspection. This means that some sites could be introduced to the programme at short notice. With reduced funding such occurrences of programme change will become more frequent, impacting more effective long-term planning.

‘Wet and dry’ skid sites identified by analysis of the SCRIM survey will be programmed and wherever possible integrated with the maintenance programmes.

The Local Asset Capital Programme (LACP)

Devon County Council has looked to breakdown some of the historic budgetary silos by introducing the Local Asset Capital Programme. Rather than budgets based on function or treatment, there has been a creation of area-based budgets which can incorporate a range of treatments, depending on the need of the area.

With the creation of the LACP process, greater emphasis has been placed on identifying and understanding local priorities when selecting works so that we can better serve.

The LACP process starts with a sample of the survey data collected:

SCANNER data,
Visual survey data, and
Customer data (throughout the year).

SCANNER data is presented as a Road Condition Index (RCI), which is deemed to appropriately represent what is found on the ground and reinforces confidence in the data.

Using this data, the process then continues by (manually) scoring sections (junction to junction) on a mobile app (junction to junction), using a 1 to 6 score, where 1 is ‘as new’ and 6 is ‘failed’ state. Whilst scoring the sections, additional details are picked up such as the use of roads and this information is added to the map as handwritten notes. Any known drainage issues are also added to the app.

This map-based information can then be shared and discussed with Parish Councils and local experts where other important local intelligence is captured. This local intelligence includes the importance of local routes with the needs of the local residents.

Parishes identify their top priorities to the Council, which are then compiled over all the county. The Council looks at the data across all the parishes and prioritises all the selected areas. Taking the upcoming year’s funding or likely funding available into account, this then results in a programme for the upcoming year.

Work is programmed for the year ahead, taking the yearly budget into account; however, about three years of work is identified in total, which will roll on into the next year’s program.

Below is a diagram illustrating the information sources used to identify schemes for the LACP.

Fig. 1:18: LACP Information Sources

There is a diverse team involved in the identification and development of the LACP. To aid operational decision making, the Council has an internal guide to the teams involved and the roles they play.

6.2 Optimising and Prioritising the Works Programme

The LACP is still an emerging practice in determining the capital programme of works and may yet be developed further as learning and outcomes become apparent.

Currently, once schemes are identified by the teams, a process of optimising these schemes and prioritising them for the annual programme is followed.

The ultimate aim for this process is to identify a pipeline of work that can span 3 years, with associated prioritisation. From that pipeline it is possible to identify the top priorities that will comprise a programme of works in year 1.

As this is an emerging and organic process, work around how sites prioritisation takes place is still ongoing however, this looks to take elements from all the data sources to establish a programme that best fits the Asset Management goals of the Council, along with the needs of the local communities.

Due to the unpredictable nature of local highway maintenance, there is always scope for the annual programme to be impacted by previously unknown but urgent works. Effective prioritisation and programming of the work means that the Council is able to robustly justify any lower priority works that may need to be delayed in such circumstances.

The pipeline programme is also under regular review as conditions and other priorities may come into play.

7. Risks

Some of the risks that prevent or inhibit the Council achieving its asset management aims for carriageways are as follows:

Budget – With insufficient Capital budget the Council will not be able to manage the deterioration in the network, thus only provide reduced levels of service. This will place greater pressure on Revenue budgets and also lead to more claims, reduced customer satisfaction and reputation damage or the Council. Also, restrictions on the Revenue budgets have also placed strain on appropriate asset management. With less capacity to undertake cyclical work on the carriageway and associated assets, the expected lifespan of the carriageway is often reduced, bringing about interventions such as safety related repairs at a much earlier stage.
Increased Costs – Linked with budgets is the increase in costs to undertake the required work. In recent years, budget restrictions along with higher rates of inflation and other costs have seen a reduction in the amount of carriageway that can be treated each year. If this trend continues the deterioration rate and backlog of maintenance will increase.
Data – If inventory and other data is not kept up-to-date and relevant it will not be possible for the authority to accurately model and plan for the deterioration of the network. This will lead to misdirection of funding and misapplication of asset management principles.
Climate – Changes in climate conditions will affect the lifespan of the carriageways through increased deterioration.

8. Improvement Actions

Alongside the Highway Infrastructure Asset Management Plan, this Annex is a live document. It will be subject to continuous improvement and ongoing development with input from Council Officers and Stakeholder feedback. Areas for improvement are identified within the Annex which are summarised as Improvement Actions in this section. These Actions are aligned with Strategic Goals and are assessed as part of a wider cross-asset prioritisation process that prioritises their implementation taking account of the framework of funding and resource availability.

The actions that have been identified as being required to ensure the Carriageways asset management objectives are achieved are:

Visual serviceability inspections – This is an emerging practice which allows greater understanding of the network and some ratification of the data resulting from condition surveys. It is envisaged that this process will become more embedded in operations with agreed frequencies and scope.
Inventory data – Accurate inventory data is fundamental to achieving asset management aims. Explore improved methods of inventory collection and updating to ensure the information is accurate.
Scheme justification and prioritisation – Through the emerging LACP process justification and prioritisation has become an important element in establishing a robust programme. The Council is annually reviewing this process to ensure the schemes selected are in line with priorities set by it’s own Asset Management plans, as well as serving the community needs.

Appendix 1 – Carriageway Treatment Selection Matrix

Version Control

Version	Date	Summary of Changes
1.0	12 April 2023

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