Who
Lambeth is an inner London borough. The north of the borough fronts the River Thames and has a busy commercial zone, whereas the south is residential. Lambeth embraces a diverse population of and contains celebrated landmarks, including the South Bank Centre, London Eye, Oval Cricket Ground and Lambeth Palace.
The Code of Practice (Well-Managed Highways Infrastructure) recommends the adoption of a risk-based approach to asset management. The guidance explains how each authority should tailor their risk-based approach to meet local needs. Lambeth’s response to this guidance is to invest in highways which provide important local infrastructure and suffer from heavy usage.
The challenge
Lambeth Council engaged with Gaist after listening to a presentation at a conference in 2019. “I was impressed by how Gaist Solutions capture accurate data and tailor their service to each client”, says Mark Eaton, Highways Asset Manager at the London Borough of Lambeth. “It was important that we found a way to modernise not only our survey collections, but also find a more effective way to select schemes. We need evidence for when councillors or members of the public may challenge on our work. Lambeth need to apply robust selection criteria for its highway schemes. Gaist Solutions’ presentation represented an opportunity to match engineering knowledge with local priorities,” he adds.
Also, especially in relation to major schemes, material prices have risen with inflation, but this increase can be surmounted by looking for economies of scale. A Schedule of Rates is often priced with different quantity bands. Higher quantities are discounted, which means an authority can achieve better value for money when delivering major schemes.
Therefore, Mr. Eaton explained, “the London Borough of Lambeth set the minimum major carriageway scheme size at 1000 square metres. If two neighbouring highways are in a poor condition and separated by less than 50 metres, they can be merged into a single major scheme, but only if the combined measurement is at least 1000 square metres. This approach balances the option of resurfacing smaller carriageways with the need to deliver value for money”.
The solution
Following a competitive tender process to undertake a borough-wide carriageway condition survey, Gaist was chosen on the basis that it would provide the council will the service and tools it needs to further improve the surveying element of its asset management strategy with a view to driving more efficient ways of working and improving its approach to scheme selections. As well as the survey, Gaist were also asked to provide a list of scheme recommendations as part of its professional services offer.
“The information we got back from the survey was incredibly detailed and accurate and nothing like we have ever had before. The data was much more granular, the colour grades were easy to assess, and the imagery was impressive,” says Mr Eaton.
Gaist bases its carriageway condition grades on the identification of damages types. They apply a lifecycle modelling toolkit to measure the future impact of the damage types. For example, the toolkit assesses which type of crack indicates a structural defect and calculates its future deterioration rate.
The polygons are divided by the extent of damage rather than by uniform linear distances. Gaist Solutions’ approach defines defective areas rather than the performance of a set length. They use an algorithm to assess all the damage types and compute a condition grade for each polygon.
“We also developed a prioritised list of rejuvenation schemes. Only a small number of locations in Lambeth were identified as being suitable. Therefore, a rejuvenation programme can be developed when Lambeth’s highway network is better than its current condition. More capital investment is needed before this cost-saving approach can be explored.”
The scoring system helped Lambeth’s scheme identification process which combines a localised collection of small sections to generate the optimal minimum area. To be considered a viable scheme, most of the combined area must have condition grades of either 4 or 5. Highways which satisfy this prerequisite will be given points. Those highways which do not achieve this standard will score zero points and will not be considered for the programme.
Lambeth also gave Gaist information on all the council’s reactive repairs for the previous three years. This included details on road classifications and key amenities in the area including schools, places of worship, libraries, transport hubs and cycle routes etc. Gaist match this data to the information from the road condition survey and produced a point-based scoring analysis to enable Lambeth to prioritise works in the area and a more risk-based approach overall for its asset management.
“Every highway in the network hierarchy is classified by how it distributes traffic. Surfaces with high volumes of traffic depreciate faster than those with low amounts of traffic. Highways with high volumes of vehicular traffic also have great volumes of pedestrian traffic. This correlation is due to the presence of shops and bus stops along these busy routes”, according to Mr Eaton.
“The reliance on these accommodating routes means that they should be maintained to a serviceable standard. Otherwise, the highway network will be unable to support transportation. The key routes are supplemented by buses, which put additional demands on those carriageways. They also have several junctions, which link users to their final destinations. Therefore, road classification is a factor in scheme selection,” he adds. “We also assess highways with amenities, such as schools. These highways not only depreciate quicker due to high volumes of traffic, but their popularity also presents a greater exposure to damage. Their high usage suggests a greater risk of compensation claims than those without amenities.”
Lambeth promotes cycling as a form of sustainable travel. Cyclists are vulnerable to poor carriageway conditions, especially potholes. Cycling accidents can result in life changing injuries. Recognisable cycle routes attract high volumes of cyclists. These highways need to be maintained to a serviceable standard. Therefore, cycle routes were awarded points.
“Not only did we have in our hands more detailed and accurate data to enable us to prioritise works but the Gaist system meant we could present this very transparent process to our Members and public in a way we hadn’t been able to before and now we are building up stronger data to work on future lifecycle analysis which means we can work more closely with our contractors to accurately price and plan works,” said Mr Eaton.
“This prioritisation method allows Lambeth to take a risk-based approach to asset management. The risk assessment measures the likelihood and consequences of asset failure. The risk is greater for highways which are in a poor condition and have a high volume of users. Investment in this way will support Lambeth’s transport infrastructure, which is fundamental to economic growth. This form of maintenance will reduce reactive maintenance expenditure, decrease complaints and mitigate the risk of compensation claims,” he added.
Gaist has now been commissioned to perform a footway condition survey of the entire highway network. They will soon provide another list of potential schemes.
