Rise in EVs could have implications for car park structures

May 26, 2023

The rise in popularity of electric vehicles (EVs) is generally a positive step. It’s one way we can help reduce our carbon footprint, while still allowing us the freedom to get around.

As we progress towards ending the sale of new fossil-fuel vehicles and hybrid vehicles in the UK by 2030, EVs of all shapes and sizes will eventually dominate the vehicle fleet.

Of course, new technologies require a rethink of different aspects of our infrastructure systems. For EVs, there the creation of charge point infrastructure, the impact of additional usage on our power networks and, while this may not seem obvious at first, there are car park structures too.

Yes, car park structures. When EVs were first introduced, they were essentially city cars, with a relatively short driving range. To increase desirability, manufacturers have had to offer more – a wider choice of models and an extended range between re-energising.

Chris Whapples is a structural and parking consultant with Stripe Consulting

To achieve this greater power, resource is required and vehicles are being designed to house the largest battery that will fit between the front and rear axles. And batteries – are heavy. They are around 10 times heavier than the same volume of fossil fuel and three times heavier than an aluminum engine. And this additional weight needs to be considered against structures, such as car parks.

In 2018, the ICE published the second edition of the Recommendations for Inspection, Maintenance and Management of Car Park Structures which requires the structure, cladding and edge protection to be assessed structurally against current design standards. But, do these design standards adequately reflect the rapidly increasing weight of large electric vehicles?

When the first edition of the design standards multi-storey and underground car parks was published in 1976, the average weight of the vehicle fleet was considered to be 1,500kg and the maximum gross weight for design purposes was 2,500kg.

The bestselling car in 1976 was a family saloon, the Mk 3 Ford Cortina. Its kerbweight (empty car with a full tank of fuel) was approximately 980kg and the gross weight (including passengers and luggage) was around 1,300kg.

Currently the Tesla Model 3 is the best-selling EV family saloon. Its kerbweight is around 1,800kg (depending on the capacity of the battery) – almost twice as heavy as the Mk3 Cortina.

Large electric cars which are coming on stream have a kerbweight of around 2,500kg and the larger SUVs can be over 2,800kg, which with the addition of passengers and luggage the gross weight can exceed 3,200kg. The average weight of vehicles has therefore rapidly increased from 1,500kg to 2,000kg.

The design standards are based on vertical loading intensity and horizontal loading intensity. These take into account the weight of the vehicle sitting stationary and also the increase in weight while it is in motion. To this day, neither the design vertical loading nor horizontal loading intensity base levels have changed.

It seems sensible, therefore, that we have a discussion about how the intensity figures are calculated. And, that we look to increase the design vertical and horizontal force figures to recognise the increase in average and maximum vehicle weight.

There is work being undertaken by the Institution of Structural Engineers. The Design Recommendations for Multi-storey and Underground Car Parks are being updated for publication in the spring of 2023. It will be a complete rewrite and update of the standards.

As well as the weight issue, it will address other issues, such as zero carbon construction; accessibility; suicide prevention measures; and fire considerations following the 2018 Echo Arena MSCP fire in Liverpool.

Updating the standards would help ensure that any new car park structures are being future-proofed. Of course, we must also consider how best to retrofit existing structures.

Currently, for simplicity, the installation of charge points tends to be in one location, thus putting all the heavyweight vehicles together, rather than randomly distributed throughout the car park. This could cause overloading in certain areas. Also many vehicle manufacturers have plans to offer fully autonomous vehicles by 2030, which will be capable of parking closer together. As a result, the loading on car park decks will further increase.

The increase in loading has significant implications for existing car parks, especially older ones which may have been weakened by structural deterioration or have issues of concern. Should the structure fail, it would be difficult to blame the owner or driver of the vehicle and the onus would be on the owner/operator of the car park to ensure that it is safe.

The new design standards should require existing car parks undertake a structural appraisal, to ensure that they are of sufficient strength. If the factor of safety is found to be inadequate, it may be necessary to undergo a regime of strengthening, but if this is too expensive then a weight limit will need to be imposed on entry. This could be by the use of signage or some form of electronic tagging.

None of these issues are insurmountable and certainly there is no cause for immediate alarm. But, it does highlight the need for us to be constantly reviewing and updating our standards. New technologies are being used all the time, and it’s important that we continually assess and reassess how these impact on our existing infrastructure systems.

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