Electric vehicle charging design and installation considerations for cable channels embedded within the pavement

By: Craig O’Neill BEng(Hons) MIET and EUR ING Graham Kenyon BEng(Hons) CEng MIET    

Introduction – NET zero 

NET zero is in full swing and electric vehicle (EV) sales are rising fast. Petrol forecourts have been used for years to fuel vehicles under safe, heavily regulated safety standards, but because of the way electricity is distributed and priced in the UK, alternative methods are being sought. 

This means more people will want to have their own charger at home. This is a simple thing to install in most cases if you have off-street parking. However, if you do not have off-street parking then it becomes a challenge.  

To help as many people as possible charge at home on their own tariffs, many local authorities, with support from the government, are proposing to allow a section of the pavement to be cut out and a channelling system to be installed, enabling the homeowner to charge their vehicle from their own property, across the pavement.

This is designed to solve the obvious trip hazard created by a charging cable over the pavement. However, trip hazards are not the only hazard to consider here. This article will examine the other considerations that need to be made.  

Prior planning 

Legislation and standards 

Any works on the highway/roadway need to comply with legislation and standards. Some of the relevant legislation is discussed in brief below. This is not exhaustive and will change depending on location in the UK. Contact your local authority for guidance.   

Highways Act 1980 (England and Wales) 

This is the main legislation governing the use of pavements. 

Roads (Scotland) Act 1984 

Fulfils a similar purpose to the Highways Act 1980. 

Roads (Northern Ireland) Order 1993 

All roads in Northern Ireland are managed by the Department of Infrastructure (DfI Roads). 

New Roads and Street Works Act 1991 (NRSWA) 

A Section 50 licence is required for individuals or third-party installers to place apparatus (cross-pavement channels) in the street. Sections 60, 65, 70, 75, 81 and 82 state the requirements for the maintenance, reinstatement and liability of works in the street. 

Town and Country Planning (General Permitted Development) (England) Order 2015 

Schedule 2, Part 2, Class E governs the installation of charging points. Planning permission is required if the installation is not considered “permitted development”. 

Traffic Management Act 2004  

This sets out requirements for obtaining a permit from the local highway authority for works on the highway. 

Construction (Design and Management) Regulations 2015 (CDM 2025) 

The CDM 2015 regulations govern the planning, management, and health and safety aspects of the installation of cable channels embedded within the pavement, as they involve breaking into the public highways. These regulations ensure that the installation of recessed cable channels is safe, durable and does not create hazards for pedestrians or unauthorized obstructions on the highway. 

Health and Safety at Work etc. Act 1974 (HASAWA 1974) 

Whilst this act primarily governs the workplace safety, its principles of risk management are applied by local authorities to public spaces, leading to the prohibition of loose cables and the promotion of approved, flush mounted, safe channel solutions. 

Electricity at Work Regulations 1989 (EAWR 1989) (Northern Ireland 1991) 

The EAWR 1989 enforces strict safety standards for electrical equipment, aiming to prevent danger, fire and shock when using a residential power supply to charge a vehicle on the public highway. These regulations, which apply to all electrical work activities, dictate that any cross-pavement solution must ensure the electrical system and cabling are safe, properly insulated, and protected from environmental influences.  

The Building Act 1984 and Building Regulations 2010

(England and Wales (although devolved to Welsh government)) 

Part P (Electricity Safety in Dwellings)

Applies to fixed electrical installations. Cables and connection from the home to the pavement channel must be installed by a competent person in all cases, either as a member of a competent person scheme or notified to the local authority building control. The work must meet the IET Wiring Regulations, BS 7671:2018+A4:2026, covering wiring systems, circuit protection and earthing arrangements. 

Part S (Infrastructure for Charging Electric Vehicles)

Requires that new or renovated residential buildings with associated parking facilitate EV charging. If a cross-pavement channel solution is part of a “major renovation” of a building with more than 10 parking spaces, this regulation states the provisions. 

Part M (Access to and use of buildings)

Requires the pavement and charging solution to remain accessible and safe for all users, including those with mobility or visual impairments, minimizing trip hazards.

The Welsh government approved documents can be found here. 

Building (Scotland) Act 2003/Building (Scotland) Regulations 2004

(Scotland) 

Domestic/non-domestic Building Standards Technical Handbook is used in Scotland 

Building Regulations (Northern Ireland) Order 1979/Building Regulations (Northern Ireland) 2012 

Northern Ireland technical booklets are similar to approved documents in England and Wales and can be found here. 

Standards and guidance

EV charging equipment should be installed in accordance with the following standards and industry guidance: 

• BS 7671:2018+A4:2026 Requirements for Electrical Installations, IET Wiring Regulations, 18th Edition 
• IET Code of Practice for Electric Vehicle Charging Equipment Installation, 5th Edition 
• IET 01:2024 Open combined protective and neutral (PEN) conductor detection devices (OPDDs) 
• BS EN IEC 61851 series Electric vehicle conductive charging system 
• Highway Electrical Association Guidance Note Electric Vehicle Charge Point Touch Potential. 

Standards for cable channels embedded within the pavement  

There are currently no dedicated standards for cable channels embedded within the pavement. The channel has to resist impact and loading from vehicle movement, temperature variance and expansion rates of materials, corrosion resistance, resistance from ultraviolet effects from the sun and other external influences.

Similar products exist, such as drainage gulleys or channel drains which utilize the standard BS EN 1433, but it is currently up to the designer to decide whether using it is appropriate alongside the potential hazards created by the charging lead. Standards for cable containment products, such as the BS EN 50626 series for conduits buried in the ground, include tests for mechanical strength (resistance to compression, impact and bending) and flame propagation.

However, as these products are usually buried at depths to protect against frost-heave, they do not include tests for direct loading, or resistance to freeze-thaw. 

BS EN 1433 includes tests for loading and resistance to freeze-thaw and direct loading, but does not include tests for flame propagation, and resistance to compression, impact and bending. 

Equally, there is no specific cable factor data relating to cable channels embedded within the pavement directly exposed to the elements.  

BS 7671:2018+A4:2026 scope 

When considering cable channels embedded within the pavement, the question arises of whether this is inside the scope of BS 7671:2018+A4:2026 or not. BS 7671:2018+A4:2026 is for electrical installations and would usually stop at the charging point socket-outlet. 

Only a court of law can provide a definitive interpretation of a standard, and determine whether it ought, or ought not, to apply in particular circumstances.

BS 7671:2018+A4:2026 does not prohibit plug and socket-outlet combinations, and the use of connector products, in an electrical installation. The fact that a permanent cable management facility is installed might lead a court to decide that a cable channel embedded within the pavement is, or ought to be, considered part of an electrical installation. 

Section 722 contains provisions of protecting the user of the charging equipment from open protective earth and neutral (PEN) faults which would affect the user if touching the car, so BS 7671:2018+A4:2026 already considers items of equipment past the charging point.  

In addition, vehicle to grid is coming in the near future which would almost certainly place it in the scope of the IET Wiring Regulations. 

Similar cases 

There is precedent for liability where socket-outlets are supplying long-term loads via a plug-in arrangement, as seen by the case of Christopher Stanley Smith v Turney William Logan & Anor where a permanently installed extension lead was considered the cause of the fire that spread to the neighbouring property. 

Permissions and role of the local authority 

In most areas, local authorities have adopted the highways and so liaising with them is the first step in applying for one of these solutions.

They will have their own procedures and checks that a resident must fulfil. The government has recently consulted on adding these solutions to permitted development. Although, at the time of publishing this article, those results have not been published. The government has, however, released some guidance on the key points for local authorities to include in their procedures[1]. 

The government have also included this document for reinstating the pavement after installation as part of the Section 50 requirements[2]. 

Unadopted estates 

Some housing estates are not adopted by a local authority and instead are maintained through a management company.

Each estate can have variance in the arrangements of proceeding with a cross-pavement charging solution, therefore, understanding who the dutyholder is and what permissions may need to be obtained is important to avoid any future liability claims.  

Trees and utilities 

It is quite common to have tree-lined streets in the UK, some of which will foul a proposed route for a cross-pavement channel.

It is important to contact the local authority or landowner on unadopted estates for advice. Many trees are protected legally and cutting through roots could cause instability or death of the tree. It is not a decision for an electrician to make. Care must be taken to avoid other services and utilities.

Electrical design considerations 

Simultaneous contact assessment 

Section 3.5 of the IET Code of Practice for Electric Vehicle Charging Equipment Installation, 5th Edition provides information about simultaneous contact and how to assess this.

It is important that any exposed-conductive-part surfaces that are connected to different earthing systems remain separated, to prevent simultaneous contact of a person between them. This is a fundamental regulation as stated in Regulation 411.3.1.1 of BS 7671:2018+A4:2026. 

Figure 1: Excerpt from BS 7671:2018+A4:2026, Regulation 411.3.1.1 

This regulation protects contact from hand-to-hand for several reasons, as listed below. The simultaneous contact assessment is to ascertain whether it is possible to make contact between the exposed-conductive-parts of the charging equipment/vehicle being charged and any exposed-conductive-parts or extraneous-conductive-parts connected to any other earthing system. This is to prevent electric shock caused by hand-to-hand contact. Examples of causes are: 

• Low voltage (LV) earth faults from one system to another: if a person is touching two different earthing arrangements and one of the earthing arrangements has a fault, then some current will pass through the person to the other arrangements causing electric shock 
• An open PEN fault on one system to another: an open PEN conductor event will raise the potential of any connected metalwork in a TN-C-S system. Like the situation above, a touch voltage will appear between the two earthing systems and a person touching both will receive a shock 
• High voltage (HV) faults: Section 442 of BS 7671:2018+A4:2026 covers the regulations of earthing systems of HV and LV. Whilst Regulations 442.2.1 and 442.2.2 are deemed to be fulfilled if connected to a supply at low voltage from a system for distribution of electricity to the public (Regulation 442.2.3), it will not be considering the situation of two simultaneously accessible LV earthing arrangements, as these regulations would assume compliance with Regulation 411.3.1.1 
• Transient surges can occur from nearby lightning flashes, switching of loads and from HV networks via capacitance to Earth. This means if someone is touching two different earthing arrangements, they can receive a shock in these situations 
• The possibility of creating a path for diverted currents: current can flow in earth paths due to leakage from equipment in the installation, or from the result of a broken PEN conductor as explained 
• Parasitic differences in potential, which can cause a startling shock. 

Open PEN faults are not the only thing to consider. For these reasons, the IET Code of Practice for Electric Vehicle Charging Equipment Installation recommends a minimum distance of 2.5 m between simultaneously accessible earthing arrangements. 

Therefore, if installing a cross-pavement charging solution, the usual simultaneous contact assessment is required. It is also worth noting that some street furniture may be Class II rather than Class I. An example of this is certain ticket machines. 

For a house with a TT earthing arrangement next to a house with a TN-C-S earthing arrangement, it may not be possible to install these cross-pavement solutions safely. 

In the example shown in Figure 2 below, the following equipment with exposed-conductive-parts would be considered simultaneously accessible according to BS 7671:2018+A4:2026, and is required to be connected to the same earthing system: 

• Electric vehicle 1 
• Electric vehicle 2 
• Metal lighting column or illuminated road sign marked 1 
• Metal lighting column or illuminated road sign marked 2 
• Metal lighting column or illuminated road sign marked 3. 

Typically, only the local distribution system operator (DSO) will know whether supplies for street furniture and lighting are connected to the same earthing system as the supply to the premises in which the electric vehicle supply equipment (EVSE) is to be installed. 

The Highway Electrical Association Guidance Note Electric Vehicle Charge Point Touch Potential  assists those carrying out simultaneous contact assessments for on-street charging. 

Figure 2: A plan of a simultaneous contact assessment 

Table 1 summarises the considerations for simultaneous contact, based on the earthing arrangement of the installation. 

Table 1: Supply earthing arrangements and considerations for simultaneous contact assessment.

BS 7671:2018+A4:2026 terms conductive parts that are in contact with the ground, that are not part of electrical equipment, as extraneous-conductive-parts. Examples might include: 

• crash barriers 
• metal fences 
• metal bollards (with no internal electrical equipment). 

BS 7671:2018+A4:2026 only requires connection of extraneous-conductive-parts to the earthing system of the electrical installation within buildings. Outdoors, most extraneous-conductive-parts can be omitted from the simultaneous contact assessment. 

However, there are some extraneous-conductive-parts that require special consideration, because they are connected to earthing systems of HV electrical installations, or because they are solidly connected to exposed-conductive-parts of electrical equipment.  

Examples of extraneous-conductive-parts that might need to be considered include, but might not be limited to: 

• metal fences of HV substations or grid-scale energy storage sites 
• metal fences associated with electric railway infrastructure 
• metal fences on which LV  luminaires with exposed-conductive-parts are installed. 

If in doubt, the owner of such extraneous-conductive-parts should be consulted as part of the assessment. 

Current carrying capacity 

The current carrying capacity of a cable is dependent on the insulation’s temperature being maintained below its safe operating temperature. Any excessive temperatures beyond the safe operating temperature will drastically shorten the life of the cable. Increased terminal temperatures at connections can eventually cause danger in the form of electric shock or fire. 

The cable used for EV charging leads must conform to BS EN 50620:2017+A2:2024. BS 7671:2018+A4:2026 does not contain correction factors for cables installed in shallow depth metallic channels in tarmac or any other pavement surface.  

The BS EN 50620:2017+A2:2024 standard contains some information for current carrying capacity. Table 2 includes information for Mode 2 and 3 charging from Table E.2 of BS EN 50620:2017+A2:2024. Most of these schemes would only be authorized by the local authority or estate dutyholder for Mode 3 charging. 

Table 2: Table E.2 from BS EN 50620:2017+A2:2024 

The table provides correction factors corresponding to various ambient temperatures. In direct sunlight, tarmac can reach temperatures of 40 to 50 °C during hot and sunny days, possible exceeding 50 °C on south-facing gradients[3]. By applying correction factors based on these temperatures, it has a dramatic effect on the current rating of the cable.

This is only on hot sunny days and in winter the effects of this will be much less dramatic. Caravans and marine hook ups also have similar cables used in direct sunlight with little ill effect. However, an EV will be drawing current for long periods of time and although most charging would ideally be taking place overnight, some people may need to charge during the day if they can get a space outside their home, or if their electrical tariff off-peak hours are during the day.

More research is required into the effects of the cable temperature when surrounded by heated pavement surfaces in a shallow metallic channel due to direct sunlight.   

Table 3 and Table 4 show the suitability of cross-sectional area (CSA) of cables to BS EN 50620 for single-phase and three-phase charging, considering a potential onerous correction factor of 0.81 to take into account the confinement of the shallow duct plus the temperature (see note 3). 

Table 3: Maximum charging current of single-phase charging cables to BS EN 50620 in gulleys

NOTES to Table 3: 
(1) At an ambient temperature of 30 °C. 
(2) Taken from Table E.2 of BS EN 50260:2017+A1:2019. 
(3) Estimated from the ratio of current-carrying capacities between Reference Method B* and Reference Method C* in Table 4D5 of BS 7671:2018+A4:2026. 
 
Table 4: Maximum charging current of three-phase charging cables to BS EN 50620 in gulley

NOTES to Table 4:
(1) At ambient temperature of 30 °C.
(2) Taken from Table E.2 of BS EN 50260:2017+A2:2024.
(3) Estimated from the ratio of current-carrying capacities between Reference Method B* and Reference Method C* in Table 4D5 of BS 7671:2018+A4:2026. 

Voltage drop 

Voltage drop is the function of current and impedance. An increase in cable length or an increase in current will result in an increased voltage drop. The EV charging point supply cable will have this calculated by the installer to ensure the cable size is adequate to deliver the required voltage. The installer would not have allowed for the charging lead itself. It is noted at the bottom of Table E.2 of BS EN 50620:2017+A2:2024 that voltage drop needs to be taken into consideration. 

BS EN ISO 17409:2020 Electrically propelled road vehicles. Conductive power transfer. Safety requirements states that:

Figure 3: Excerpt from BS EN ISO 17409:2020 

Table 5: Maximum length of single-phase charging cable to BS EN 50620 from EVSE to EV based on total voltage drop assuming a maximum supply voltage variation of U₀-10 %.

NOTES to Table 5:
(1) Takes into account the increase in effective load current of constant power loads at maximum voltage drop, in comparison with the effective load current of a linear load at maximum supply voltage.
(2) Voltage drop at 60 °C taken from Tables 4F1B and 4F3B of BS 7671:2018+A4:2026.
(3) Maximum length of cable due to voltage-drop exceeds 40 m. Charging cables longer than 40 m are not recommended. 

Table 6: Maximum length of three-phase charging cable to BS EN 50620 from EVSE to EV based on total voltage drop assuming a minimum supply voltage U-10 % 

NOTES to Table 6:
(1) Takes into account the increase in effective load current of constant power loads at maximum voltage drop, in comparison with the effective load current of a linear load at maximum supply voltage.
(2) Voltage drop at 60 °C taken from Tables 4F1B and 4F3B of BS 7671:2018+A4:2026.
(3) Maximum length of cable due to voltage-drop exceeds 40 m. Charging cables longer than 40 m are not recommended. 

Open Pen Detection Devices (OPDDs) 

OPDDs are only recognized in BS 7671:2018+A4:2026 for disconnection of an EV due to open PEN faults. 

OPDDs have sometimes been cited to mitigate against simultaneous contact. This is not true. IET 01:2024 is currently the only standard for OPDDs. 

An OPDD to IET 01:2024 is not tested for its ability to mitigate against the full range of situations that may occur through simultaneous contact and not complying with Regulation 411.3.1.1 of BS 7671:2018+A4:2026. The scope of IET 01:2024 states that: 

“The functionality of OPDDs is intended to protect persons and livestock from the resulting issues relating to a continuity fault in the PEN conductor, such as, electric shock and thermal effects when employed in 230 V AC single-phase, 230/400 V AC three-phase and 230/460 V AC split-phase supply systems.” 

The full range of potential implications from simultaneous contact between different earthing arrangements have therefore not been considered. This is to be expected, as Regulation 411.3.1.1 of BS 7671:2018+A4:2026 requires simultaneously accessible exposed-conductive-parts to be connected to the same earthing system (see above). 

M1a and M1b are methods of operation according to IET 01:2024 and both monitor line to neutral voltage. On a three-phase distribution main (most common), the neutral voltage with respect to Earth on the consumer’s side of a broken PEN will depend on the sum of all resistances to Earth such as extraneous-conductive- parts, distributor’s electrodes and consumer electrodes, and the unbalance of loads on the distribution main, across all the installations on the consumer side of a PEN fault.

The larger the imbalance, the larger the touch voltage. It is important to note that whilst OPDDs may help control the risk of a touch voltage rising higher than 70 V because of an open PEN fault, there are conditions in which the touch voltage exceeds 70 V and the OPDD does not operate. This risk can be reduced by the adoption of method M3 in conjunction with method M1a.

The problem with method M1a is that it does not align with thresholds in Energy Networks Association (ENA) Engineering Recommendations G98 and G99 and therefore, is considered incompatible with vehicle to home and vehicle to grid applications. Whilst M1b allows more range of voltage, the possibility of having a touch voltage >70 V but not operating is intolerable, so must be used in conjunction with protection method M3. 

Figures 4 and 5 illustrate that there are possible areas of the diagram where the neutral to Earth touch voltage may rise above 70 V and the OPDD will not operate. It should also be considered that, in a real open PEN fault, the neutral voltage is constantly changing as the balance of loads on the phases changes, and therefore, it is likely that the fault would be detected by methods M1a or M1b at some point.  

It is also important to note that under some rare fault conditions with extreme power factor or harmonics, it is theoretically possible for the neutral to Earth voltage to rise to nominal voltage level (U₀). 

Figure 4: Excerpt from IET 01:2024 shows a phasor-space diagram comparing the thresholds of line to neutral voltage for method of operation M1a and of areas where the voltage may exceed 70 V but the OPDD does not operate 

Figure 5: Excerpt from IET 01:2024 shows a phasor-space diagram comparing the thresholds for line to neutral voltage for method of operation M1b with a touch voltage of 70 V

Method M3 is a way of mitigating against the potential blind spots of methods M1a and M1b. This does not avoid the other issues associated with simultaneous contact of different earthing systems.

Whilst having type M1b and M3 methods as per IET 01:2024 is certainly “a nice to have”, the M3 part will only operate once a person is already receiving a contact shock. It is important to understand that OPDDs to IET 01:2024 are detection devices that reduce the probability of a dangerous shock, although cannot fully protect from it in all scenarios.

So, whilst these detection devices reduce the probability of a dangerous situation, they are not the same as a protective device that we are used to such as residual current devices (RCDs). An OPDD has only been considered for a certain scenario and not for simultaneous contact between different earthing systems.  

Operational considerations 

Maintenance 

Maintaining any electrical lead is essential for long term safety. Charging leads left in cable channels embedded within the pavement will be subject to dirt build up, damage from rodents, foxes, etc. and over time, subjected to lots of extreme temperatures.

It would be prudent to remove the charging lead after each use and ensure it remains debris free but, on cold, icy and wet mornings, when the lead is muddy or has been fouled by one of those animals, it may be extremely tempting to leave it there. It is extremely important to check the lead carefully before each use, especially if stored outside to visually inspect for damage. 

Software solutions 

Some companies are developing software that could be used to share charging equipment in a street to help alleviate the issue of not being able to park outside.

The idea is to use your neighbour’s charger and input your own code to link the cost to your own tariff. These are sometimes called peer-to-peer EV charging solutions or simple rental schemes. These software solutions also have the ability to help find a free charger in your area. 

Summary 

• It is important to try to find ways for more people to charge their EV at home
• This is not a quick fix solution; it is a carefully engineered long-term solution to aid the particular property in question charge an EV 
• Method M3 of IET 01:2024 cannot be used as mitigation for simultaneous contact across different earthing systems 
• Current carrying capacities on hot days need careful consideration to avoid damage to the charging lead and connections to both the charging equipment and the car 
• Voltage drop could be a consideration in locations of low voltage drop or using some methods of OPDD 
• Liability needs careful consideration regarding the design, use and future ownership.  

References 

[1] Department for Transport and Office for Zero Emission Vehicles Cross-pavement solutions for charging electric vehicles 

[2] Department for Transport Specification for the Reinstatement of Openings in Highways- Electric Vehicle addendum

[3] Highways Agency The behaviour of asphalt in adverse hot weather conditions, 2001 

Acknowledgments 

• Joe Cannon MSc CEng MIET  
• Calum Mansell IEng MIET 
• Michael Peace CEng MIET 
• Rupert van der Post MBA BSc CEng MIET 
• Susannah Girt.