E.K. James, E.D. Lawrence

Highway Maintenance Planning and Network Management

Many local highway authorities in the UK are now undergoing major organisational changes and severe budget restrictions. This, when linked to increase in traffic, environmental pressures on new roads and public expectations for travel, demands a system that gives maintenance planning engineers the means to manage this complex process.

It is the intention of this paper to emphasise the need for highway maintenance and the fact that the maintenance must be planned, progressed and recorded. Computer systems over the last one and half decades have tackled this problem in a textural way and many gave sterling service. To derive the greatest benefit from highway survey data an integrated GIS/RDBMS is essential.


Many local highway authorities in the UK are now undergoing major organisational changes and severe budget restrictions. This, when linked to increase in traffic, environmental pressures on new roads and public expectations for travel, demands a system that gives maintenance planning engineers the means to manage this complex process.

Highways Image

Kent HMMS (Highway Maintenance Management System), an application using ArcInfo, is such a system. It enables the many aspects of highway network management, i.e. surveying, planning and design to be integrated into a single package. Analysis of data from various sources can be used to help balance these pressures and produce statistical information in support of budget bids. The key to all this is a highly intelligent network coverage with multi access points for interrogation which is understood and used properly by staff with the appropriate skills.


Highway maintenance is about keeping the roads safe for all users. The cost to any community of accidents cannot really be measured in pounds and pence.

Flipped by a defect kerb

Any reduction in accidents, of any severity, is to be striven for. A maintenance ethic that targets poor road condition, surfacing or design and spends the allocated funds accordingly will, eventually, have an effect on road safety.

Poor Road Condition

The days, for the foreseeable future, of ad hoc surface dressing or laying a wearing course to improve the visual condition are a thing of the past. Maintenance funding in the future will need to show a benefit to the public in some tangible form.

Modern highway maintenance should try to achieve two main goals:-Protecting the present - this is best described as the everyday ongoing maintenance aimed at holding the network at its present condition. Pothole repair, haunching of road edges, surface dressing, verge cutting, sign and light repairs etc. This form of maintenance is fairly low cost and effective when targeted correctly.

Strengthening for the future - this is the more costly option and therefore requires more information, expertise and systems to be able to target accurately where the now limited funds should be spent. The structural condition of the network and its future well being will depend on where funds are allocated NOW.


All highway maintenance engineers have a story to tell of insurance claims against the highway authority for some maintenance lapse or other. Kent County Council Highways Department have a "Road Squad" whose duty is to repair reported defects within a specific time depending on the category assigned by management. This gives the public access to the "emergency" system and allows highway managers to categorise the defect before taking action. The system, although effective, is expensive and coupled with even larger emergencies, such as collapses, can eat away at limited funds.

Emergency Road Repair

Good maintenance is pre-planned, which means budgeted, properly funded and supervised. It is maintenance planning to which the Kent HMMS system is aimed and can be best summed up in the phrase:-

Predicting Future Maintenance Needs!

It is said that a picture is worth a thousand words. Kent HMMS takes the thousand words of complex technical data and creates a picture that helps non technical administrators to understand the technical process. To be able to follow this process through, data must be collected, processed and be made readily available to all end users. The final message should be clear and easily understandable to both engineers and lay people. This approach can have a major effect on budget allocations. It is essential the system does not remove from the engineer the decision taking. The trends section of the module can be extremely useful in identifying possible future trouble-spots and, of course, prevention is better (cheaper) than cure.



The network started life as a text based node and section network design, instigated by the DoT, which used the nodes as the connectivity point. Data was captured by measuring from a node as chainage and cross sectional position. This system worked well to create text reports and computer output of the data but not everyone, however, understood the referencing system, including the data collectors in many cases.


It became obvious that a geographical system was needed to best display the data now available. To give the network spatial value the highways were digitised and the existing chart reference made a prime attribute of the new spatial arc. The network has been refined over the last 8 years and now is a highly accurate representation of all adopted roads in Kent. Upgrades to the network take place using both the GIS and CRS (Chart Referencing System) modules. GIS maintains the spatial integrity and CRS ensures that node and section IDs are unique and a historical record is maintained. This record becomes part of the version control used by GIS to display historical data against a valid network.


The chart referencing system as previously said, is not readily understood by all. With the advent of the NSG (National Street Gazetteer) it is envisaged that in time the NSG number will be the prime attribute along with relevant nodes. The connectivity between nodes would be by ESU (Elementary Street Unit) making the network even more usable and allowing the system to be operational anywhere in the UK. Use of GPS to set up a network would enable the system to be used anywhere in the world.


The control of network editing is extremely important if the integrity of the data is to be maintained. It is essential that each update should be undertaken on all databases at the same time, given a version number and date stamped. To ensure this happens all amendments are made on a scratchpad as they happen and the network manager is given the task of "going live". This allows editing on the scratchpad to take place over a lengthy period if necessary without detriment to the working of the live system.


We have to know what the present is! Any system of management control is only as good as the data serving it. Poor quality, quantity or uniformity of data will bring into question any analysis of that data. Highway network management requires vast amounts of information that needs to be accessed quickly and accurately. Data can be categorised into two main sets, Inventory and Condition. This really means What is There and What State. What is there is, for the most part a static data set that only requires minor changes on an ongoing basis. What state is a constant requirement for survey data to be collected and processed to a systematic programme. This will allow forecasting and trend analysis which is explained later.

What is There - Inventory

The highway inventory is made up of many components such as carriageways, footways and street furniture. These elements can be further categorised as types, construction materials and furniture items such as signs, manholes etc. To hold this wealth of information an Ingres relational database is used with a software package called HERMIS (Highway Engineering and Road Management Information System). Kent has 10,000 km of carriageway, 6800 km of footway and over 4 million records of inventory items. In addition further attributes have been assigned to the network for specific legal and environmental requirements.

The NRSWA (National Road and Street Works Act) requires data on road category (usage), engineering difficulty (bridges etc.), traffic sensitivity (urban areas) and special road surfaces (block paving etc.). This information must be maintained and issued to the utilities in both text and graphical format.

Data on roadside nature reserves allow grass cutting schedules to be made recognising these special needs. Road works can also be monitored to help preserve these environmentally sensitive areas.

Road information signs have the additional attribute of a photograph number that links to a digital photo of the sign which is automatically displayed when the sign is selected on the screen. Data for street lighting and drainage is being collected to also include this feature.

What State - Condition

Condition surveys take place on a rolling programme and consist of structural (Deflectograph), skidding (SCRIM), texture and ride quality (HRM) and visual (DVI). The data from these surveys is stored in a Condition Assessment Module (CAM) and allows engineers to monitor the state of the road, identify trends and help select and prioritise future maintenance schemes. The data is date stamped and, therefore, a historical record of the network maintained. The module has system defaults for initial selection which can be changed by the engineer for specific scheme type.

There are three main scheme types: Surface Dressing - Protection - Strengthening.

Each has a cost/km rating and by interacting the data sets, scheme selection is made easier. A surface dressing scheme identified by the skid data would, for example, be wasted on a road with a structural life of less than 10 years, as shown by deflectograph, and therefore protection or strengthening would be required.


The previous paragraphs outlined the system and the data sets contained within. To try and explain or describe all the functions available in Kent HMMS display module would be too lengthy in this paper and it would end up like a user manual. In the introduction it was said a picture is worth a thousand words, well, the picture creator is a GIS application using ArcInfo software as the driver to bring this together. Kent HMMS is a modular system that has as its main components a RDBMS running three applications - HERMIS, CRS and CAM and a Geographical Information System (ArcInfo).

System Structure and Interfaces

Any display of graphical data can best be described as What? - Where? - How?

What to Display

The system must be capable of being selective in what is displayed. With so much data available the user can tailor the output to satisfy the client by displaying only essential items from the database. A cluttered picture can be almost as misleading as no picture at all.

What to display can be designated as network attributes or survey data. The network attributes include such items as road classification, road names, road numbers, chainage markers, network nodes or section identification and a selection of boundaries which include HMUs (Highway Management Units), Area office, parish, wards. It is often desirable to display the highway network using various attributes as the basis of the display. Selection of an attribute will display the network by say, speed limit classification or traffic volume. Historical networks can also be used for data display. The survey data includes all the survey types whether on their own or together. Inventory and condition survey can be amalgamated by the user to help identify specific road conditions (e.g. skid data at pedestrian crossings). By combining survey data with, say, chainage markers, scheme locations can be precisely identified for subsequent contract drawing production.

Where to Display

Selection of the correct area for display is essential to focus attention where it is required. The ability to go from a strategic viewpoint (county level) to precise detail (individual road/section) is fundamental to a GIS system that satisfies all its users. An area can be selected by highlighting the required menu option such as; parish, road number, section id, node or OSGR. In addition a gazetteer of all road names (17,600 in Kent) can be accessed on a county level to allow selection of an individual street. The selected item will then be brought on to the screen for future analysis etc. Data sets can be broken down into smaller sub sets to quicken access and be tailored to individual users. It would be a waste of machine space for, say, HMU 08 to hold data pertaining to HMU 11 and vice-versa. The ability to segregate data of a geographical nature is necessary when configuring the system and assessing the hardware needs of each user.

How to Display

Having selected what and where to display, there now only remains how to display. To do this the system has the ability to display lines and symbols, representing the network attributes or data, at different sizes, thicknesses, colours and shapes. This is totally user defined and is available to all sub modules within the Kent HMMS GIS system. Differing data sets can be displayed alongside one another for comparison and inventory/condition data can be displayed at the same time.


In addition to being able to determine how to display the data a CAD option allows enhancement of the display. Text can be added to a specified font, size and colour. It can be stretched, squashed, underlined, italic or bold and may be boxed to blank out background data. It may be placed anywhere with any angle of rotation. Lines can be different styles, thicknesses and colours and a comprehensive set of symbols, hatching styles and colours give the user further display capabilities.

Many aspects of preparing reports for government, council members and the public require that additional information be available to supplement the technical data from engineers. For this reason the development, in CAD, of various enhancements has been found to be of great use. Standard items such as north point, scale bar, legends and key-boxes can all be placed on the final plot.

Photographs, either scanned or from digital cameras, charts from PC applications and text in ASCII format can all be brought onto a display to add emphasis and clarity to the message. In addition the system has several display capabilities that have been developed especially for certain types of output. These facilities are menu driven and allow the user to produce hard copy that is unique to the system. As mentioned earlier certain inventory items, such as signs, lampposts, manholes, have attributes that are used to produce plots of the map area around the item, text data assigned to that item and pictures of the item. These can all be output to hard copy for including in, say, a works contract.

Sign Location Map

The NRSWA data can be automatically output to hard copy in order to create an atlas, at varying scales, and with page pointers. An index of the county gazetteer showing road name, parish, NSG number and page on which the road occurs is also part of the atlas. Updating of the atlas can be by single or multiple page amendment, all created automatically.

Example Street Works Atlas

Roadside nature reserves can be output with a location map, general description and management instructions and a photograph, for issue to nature wardens, cutting and roadwork contractors.

Roadside Nature Reserve

Data from surveys displayed on a network in a report does not always have the same impact as data in a diagrammatic form and, therefore, the ability to produce a plan or profiles, colour coded, of the survey data against a chainage can enhance the impact of a report.

Strip Diagram Example

The very nature and complexity of the data available to the system can in some cases cloud the message being sent. For that reason the facility to split the screen (and final plot output) into a multi window environment can prove to be useful in many instances. Each screen has the full functionality of the system and accepts and displays data/attributes/images and the CAD facilities. These multi screen displays can be plotted in any size from A3 - A0.

Split Screen Output

Statistical data can be derived from the system by either using the Ingres database for analysing different data as defined by attributes or ArcInfo for analysing on an area as defined by the screen or user polygon. The data can then be added as a histogram or pie chart to supplement other display options.

Statistical Analysis


All Ordnance Survey map scales are supported by the system and can be used as background to all survey plots. Display items can be selected from the vector map base whilst raster map images can be scaled to suit user/client. System defaults are set to avoid erroneous plot scales being used resulting in the loading of OS 1250 vector for the whole of the county. The system automatically selects the optimum map type to suit the present scale. The defaults can be overridden if a specific map type is required.


Any computer software package worth its salt must stay 'alive' and develop to follow new trends, take advantage of new technology and, most important of all, produce the goods for its customers. Kent HMMS is developing continuously and some of the future and not so distant future items are now briefly explained.

Maintenance Histories - is a module that allows HMUs to populate the database with details of maintenance functions they have carried out. This is anything from a pothole or gully emptying to a fairly substantial strengthening and paving exercise. This database will allow managers to build up a cost profile of the network and assess value for money. Maintenance Schemes - allows the user to populate a database with details of proposed schemes. Managers looking at the strategic viewpoint can enter future schemes which will ensure the HMUs will not waste funds repairing roads that are, unbeknown to them, already designated for major works. Construction Details - will be a database which holds details of construction materials, depths, date of construction and any other attributes considered necessary for this module by end users. Drainage - will be a subsidiary network based on manhole, soak- away and gully location that will have the attributes of pipe runs, sizes, materials etc. Imagery from CCTY, showing defect details, will be made available for output to hard copy. Lighting - will be a similar database to drainage but networking the cable runs and linking to the interactive module monitoring street lighting


The data collected and processed in the past 6 years has indicated that there is now much to be done. Trends in personal mobility, larger and heavier lorries and the number of journeys undertaken have all shown an increase in those 6 years. Road usage has been a growth area and in all likelihood will remain so until the end of the millennium at least. This increase in traffic and corresponding decrease in funding will, inevitably, lead to a deterioration of the highway network. This in turn will lead to an increase in the demand for maintenance and consequently a better, more effective way of allocating scarce resources. Accepting the fact that a modern growing economy requires an efficient, well maintained integrated transport network. It is imperative that systems are in place so that managers have the wherewithal to plan, direct and monitor the network's well-being. Decisions need to be taken on which part of the network should receive priority. Should you maintain the nationally important strategic network to the detriment of country lanes and estate roads, or satisfy the people in their homes to the detriment of commerce. The strategic network by its very nature of traffic size and volume will inevitably deteriorate faster than a less well used estate road but the balance of funding is the challenge the maintenance engineer must meet in the coming years.

The economics of maintenance and the whole life cost of repairs must be questioned and decisions taken that will not only protect the present but plan and strengthen the future.

Kent HMMS is a system that targets maintenance schemes, gives control by auditing works and ensures delivery of management objectives.

E.K. James (Jimmy)
Principal Engineer, Maintenance Planning Consultancy
E.D. Lawrence (Ed)
Group Manager, Maintenance Planning Consultancy
Highways Dept., Kent County Council
Doubleday House,
St. Michaels Close,
ME20 7BU

Telephone: +44 (0)1622 605873
Fax: +44 (0)1622 710621