Street lighting lifecycle plan

Document Control

Revision:

Introduction

Asset management is widely accepted as a means to deliver a more efficient and effective approach to the management of highway infrastructure assets through longer term planning and ensuring that levels of service are defined and achievable for available budgets. This approach supports making the case for funding and better communication with stakeholders facilitating a greater understanding of the contribution highway infrastructure assets make to economic growth and the needs of local communities.

This document outlines the lifecycle plan for the street lighting asset for Plymouth City Council outlining the approach to management and maintenance of the street lighting assets.

Context

Lifecycle planning is key to asset management and acts as a means to link the priorities identified in the Asset Management Objectives (see Asset Management Strategy) with the works being carried out on the network. Through the analysis of asset management data this process forms a framework of identifying the required maintenance activities to meet these objectives, to select and prioritise these activities into a programme of works and to then assess the effectiveness of the process in meeting the defined objectives (see below).

Asset Management Objectives:

• To provide a safe, efficient, accessible and health-enabling highway network
• To reduce the environmental impact of the highway asset
• To deliver cost effect asset management
• To encourage the adoption of innovation in the highway service

Objectives and Challenges

Plymouth Highways’ overall objective for the Street lighting asset is to undertake a programme of capital replacement of the existing old technology stock over a fixed life to move towards a more sustainable innovative asset. This approach to Street lighting is outlined in this lifecycle plan.

For Street lighting the current major issue is the structural deterioration of the ageing lighting column stock. The vast majority of columns in the City are galvanised mild steel, a percentage of which have corroded below ground level making visual detection of any corrosion almost impossible. From inspection data collected it has been identified that a large number of columns will need replacing over a 6 year period. The investment is being realised through ‘Capital Borrowing’ at a cost in excess of £8m. In support of this, Plymouth Highways has combined the structurally deficient column replacement programme with the upgrading of the lantern units on signs and Subways.

A trial ‘dimming and trimming’ programme is being introduced which will reduce the energy output of the units, this will have an effect of reducing both the overall energy consumption and the carbon output. It is Plymouth Highways objective to create a rolling 5 year forward programme plan of all schemes to underpin this.

The desirable levels of service for street lighting asset are set out in the table below, these align to the asset management objectives set out in the Asset Management Strategy.

We follow guidelines on performance outlined in the publication “Well-lit highways” (following the publication of a new code this will be reviewed) and on the criteria described in the following paragraph. Customer feedback is via the NHT annual customer satisfaction survey and pro-active direct communication. KPI measurement is locally measured and performance reviewed within Operations Board and through the Performance Management Framework.

Failure in performance runs risk to reputational and/or liability, the table below, which details the main risks.

Asset Data Management

Asset data management is the process of capturing the asset data in terms of the condition, inventory on highway assets and storing the data in a form of reliable, repeatable, and accessible source of information. This is also in line with the authorities Data Management Strategy.

Inventory Data

Accurate and up to date inventory of the asset is an important element to good asset management. Street lighting inventory data is held in Mayrise, a management tool that provides a central depository within which all important data can be uploaded and stored.

Street Lighting Assets and Characteristics

Street lighting is divided into various categories for asset management purposes. The main consideration in terms of capital investment is column type and lantern type. The following categories are used:

Column Types

Lanterns

Lantern type and manufacture differ dependant on utilisation and location – See Specification for approved listings.

Street Furniture (Signage)

Illuminated street furniture is subject to an ongoing conversion project to either a ‘reflective’ unit or LED again dependant on the location on the network and specific risk assessment. The project when complete will create a fully sustainable asset with minimal maintenance requirements and reduced energy costs

Condition Survey

Structural Testing of street lighting columns is undertaken once they reach their “Action Age”. This date is determined by the location of the column, its surface protection, wind exposure and any attachments fitted to the column. Generally the “action age” is around 20 years after installation. Steel lighting columns are visually inspected and measured with an ultrasonic material thickness tester. The Council also has lighting brackets mounted on local DNO wooden poles, bridges and other buildings and structures not owned by the council. Structural testing only ascertains if the bracket (and ancillary equipment) fixing to these structures is sound.

Note we have accelerated our structural testing programme ahead of our Capital Column replacement project in order to determine areas of priority and are selective based on allocated RAG rating. Detailed analysis of the results has shown that different types of lighting columns have different structural problems. Testing of steel lighting columns has shown considerable variability of lighting column condition in any one location. The main cause of failure is internal corrosion at point of the ‘Hot Shrunk Joint’.

A visual safety check of the condition of each lighting column is carried out on every visit. Lighting columns thought to be structurally unsound are further assessed and may be subject to an emergency “make safe” or are replaced in the shortest possible time dependant of risk. Structural testing enables programmes of work to be identified for the capital replacement project year on year.

Existing Column Stock Age Profile

Data Management

The management tools within Mayrise enable the user to search, interrogate and report on the data in order to:

• Issue, report and update Maintenance programmes.
• Review asset prioritisation, age to intervention and consequence if failure occurs.
• Produce prioritised lists of issued works.
• View GIS mapping to aid the preparation of the inspection, design and works management programmes.
• Assist in the production of the required Whole Government Account (WGA) asset valuations (Gross Replacement Cost and Depreciated Replacement Cost).
• Provide lifecycle planning.
• A Gap analysis of the data stored in order to track progress and identify missing or erroneous data.
• Build reports made up of the fields specified and /or data filters applied.

Performance Management

Key Performance indicators (KPI’s) are being developed into measure effectiveness of operation against:

Reactive Maintenance and Defect Repairs

Serious defects are generally attended to within two hours by the Street Lighting Maintenance Contractor. Sites are made safe by signing (TM) or repair.

Routine maintenance is carried out by the specialist street lighting maintenance contractor and delivery is standardised by use of Engineering adopted SLA.

Life Cycle Planning

Collect Inventory & Condition – The inventory has been collected, updated, collated and stored in the Highways Asset Management System (Mayrise).

Assess Performance – The current performance of the asset is monitored through the Highways Term Contract Key Performance Indicators.

Assess Demands & Risks – This has been identified in ‘levels of service’ to reduce energy and create a sustainable asset

Produce Investment Strategy- Street Lighting maintenance plans to enhance the Lifecycle of this essential asset and minimise Whole Life costs.

Lifecycle Whole life costs include not only the direct costs of works, design and supervision testing and inspections, but also the indirect costs caused by sub-optimal maintenance regimes, including inconvenience to users, environmental impacts and third party claims. The main factors which will affect the whole life cost of an individual installation are:

• Type and quality of Installation
• Longevity of Materials
• Degree and type of damage and degradation
• Age of asset
• Maintenance to damage and degradation
• Timing of intervention and quality of medium and long term treatments
• Environmental considerations

Historically the approach to maintaining street lighting has been:-

• To carry out electrical and structural testing of unit
• To undertake ‘night patrols’ for lighting faults
• To undertake reactive maintenance works ‘on time’ to prevent short term deterioration and keep in a safe condition.
• To maintain an up-to-date inventory of lighting stock to facilitate maintenance management and enable competitive purchase of energy.
• To replace life-expired columns within budget availability, with a particular emphasis on replacing life-expired columns based on priority.

This approach was based on good practice. However, the capital sums allocated for column replacement historically have not been adequate, resulting in a backlog of lighting columns/lanterns needing replacement. A major Capital Replacement programme has now commenced and over a 5 to 6 year period circa 12,000 lighting columns will be replaced.

Risk based approach

The risks involved in implementing the lifecycle action plan have been assessed against the below grid of likelihood versus impact and are detailed in the table below, with an outline of the mitigation to be planned.

Sustainability Options

In order to identify what treatment, material or technology to use to support the lifecycle plan for the asset it is necessary to determine and analyse the options available, from this a selection can be made to ensure that the most suitable/cost effective solution is made.

Options for different parts of the network have been developed in accordance with existing spacing, geometry of the network, current lighting requirements, maintenance liabilities and future potential burdens, the limited number of types of lighting installation, and ways in which they deteriorate, lead to a relatively short list of maintenance treatments. The temperature rendition of the lighting units selected is considered for the protection of bat habitats.  

Short-term treatments are dictated by safety and serviceability requirements. Decisions on when to intervene with medium and long-term treatments are determined in accordance with the asset management strategy and in line with our capital upgrade programme. Details of specifications can be found in the SLA for Street Lighting Maintenance and the Term Maintenance Contract Specifications (SWH).

Column Painting

New lighting columns are fully galvanised and have additional root protection, older steel columns had only aluminium or zinc spray coating which was then over-painted. The existing painted columns will continue to deteriorate and will initially become visually unsightly. Surface rust will then corrode the parent metal, weakening the structure. However, these lighting columns also corrode on the inside as the internal surfaces of the tube are not protected. Painting will not therefore significantly extend life expectancy of these un-galvanised steel columns. However columns that have previously been painted may benefit from a new coating, especially when supported by a structural survey test that indicates structural integrity is still effective.

Indicative Work Programme

The below table details the forward programme of works for the next 5 years. It is expected that during this period there will be 2000 lighting columns a year in need of replacement (pending the outcome of structural inspections), 800 lights per year on identified signs which will be upgraded to energy-efficient LED alternatives, 200 illuminated bollards to be replaced with retro-reflective alternatives to remove the energy requirement.  It is also expected that there will be an additional cost of £5000 per year for lanterns which are identified as being defective upon inspection.

Further Investment Scenario: Introduction of a Street Lighting Profiling Regime

Creating a Variable Profiling lighting strategy offers Plymouth City Council an opportunity to save a significant amount of energy and associated carbon emissions. Our suppliers have carried out a detailed survey across the UK to study the effects of adoption on strategy, comparing Traffic Collision and Crime Data sourced from police data across 62 local authorities.

The data indicates an overall reduction on traffic collisions and a reduction of Burglary, Robbery, Vehicle and Violence is evidenced when such profiling is adopted.

The argument is so pressing, especially if reduction of energy usage, CO² emission and Light Pollution is augmented into the reasoning, that many Local Authorities have already adopted or are moving towards such an arrangement, this includes our immediate neighbours (Cornwall, Devon and Exeter) as well as scalable city comparisons – (Bristol & Milton Keynes) it is reported that 85% of all local authorities now dim their street lighting installations.  

This strategy must however be based upon consideration of many variables which detailed below, these considerations are laid out in various recognised standards as well as DFT Transport Analysis Guidance (TAG).

There are four types of lighting requirements for street lighting within this consideration: - residential, commercial, retail and Main Road Networks.

The purpose of carrying out an assessment is to support the proposed profiling profiles that are to be applied and endorse the regime that is then selected for the variable lighting levels. It is recommended in the guidance that the profile regime is reflected across all classifications of roads, to this end, a review of ADT has been averaged across all road types to generate a picture of traffic movement without turning our street lighting installation ‘off’

This approach has been benchmarked against industry standards and has been reviewed by an industry expert, Matthew Lugg OBE- Head of Profession at WSP (President of the Chartered Institute of Highways and Transportation CIHT (2018-2019)) and supported by Devon & Cornwall Police.

The system is based on ‘Open Protocol’ communication arrangement which would enable other applications to the CMS system, including Emergency Services adaptation during emergencies, Monitoring of Air Quality, Road Temperature Sensors for Gritting optimisation, Traffic Data Capture, vehicle communication for semi-autonomous future proofing to be added at a future date and this is linked to our Transforming Cities Fund Tranche 2 initiative.

---