Australia Transport and infrastructure

Loosening your belt to cure obesity: Rethinking standard vehicle sizes


Photo by Mauro Sbicego on Unsplash

Standards Australia are currently revising AS/NZS 2890.1:2004 – Parking Facilities – Part 1: Off-street car parking, the standard that underpins the design of most vehicle circulation spaces other than roads. (The consultation closes November 9). The proposed amendments include enlarged standard car park sizes, reflecting underlying shifts in the so-called B85 and B99 design vehicles. These are vehicles that are supposed to represent the 85th and 99th percentile vehicles on Australian roads – in other words, 85% of vehicles are below the B85 size, and 99% are below the B99 size. The B85 vehicle, in particular, is the key standard vehicle around which buildings and car parking structures are designed.

However, cars have been getting bigger, particularly with the popularity of SUVs and large dual-cab utes, and the standard now proposes to reflect this with larger design vehicles and parking spaces.

This has, gratifyingly, received some media attention and pushback; there are dozens of comments posted to the draft new standard arguing against the change. Lewis Mumford famously compared adding lanes to roads to trying to solve an obesity problem by loosening your belt. As apt as that metaphor was – fat-shaming aside – it is even more appropriate for car parking spaces. Increasing the size of car parking spaces to accommodate ever-larger vehicles is an exercise in futility, and makes for terrible public policy. It will exacerbate the tendency to car-dominated built form and loosen one of the few disincentives to the purchase of over-size vehicles.

But, how does this play out when what is being changed is a technical standard, rather than a government policy document or planning control?

The role of the Australian standard

This situation has highlighted the ambiguous role played by Australian standards in informing public policy. The standard is maintained by Standards Australia – an independent non-government, non-profit organisation that sets technical standards used by a wide range of industries. Standards Australia note that they are “not responsible for enforcing, regulating or certifying compliance with… standards.”

It could be argued that it is not the role of a standards body to make a public policy decision about whether car spaces should be enlarged or deliberately constrained to restrict the size of vehicles – those are decisions for government. In the current standard, the B85 vehicle is compared to a Ford Fairlane, a vehicle no longer sold. Surely the standard should be updated to reflect modern vehicles and up-to-date calculations of what the actual 85th percentile vehicle size is?

It is also true that the preponderance of super-sized vehicles is a broader regulatory failure – if we want smaller cars on our roads, there are much more direct regulatory and pricing mechanisms that could be used to achieve this effect. Controls and design standards for built form are a clumsy and indirect method to regulate vehicle size.

Those are fair points; however, I would also argue that a standards body should not be naive about, or blind to, the policy implications of the standards it sets. While governments will set planning regulations about how car spaces are designed – in Victoria, this is at clause 52.06 of planning schemes, which does make some modifications to the standard’s sizes – Australian standards are treated as background documents that can inform decision-making, and designers and traffic engineers will undoubtedly rely on the new standard.

The reality is that an amended standard will be widely referenced in decision-making and design. If there is no change by governments to the way that they frame planning regulations, the increased size will likely flow through to actual practice, especially in locations where land is plentiful and cheap. This is particularly the case because planning controls implicitly treat design standards for car parking spaces as minimum sizes – the regulations assume that the problem they are trying to avoid is undersized spaces. Controls framed in this way will not be sufficient to prevent parking bloat.

The risk, therefore, is that the standards review becomes a policy decision through neglect. The standards decision is waved through as a simple reflection of empirical reality, and planning practice then falls in line with the standard, either through regulations being updated based on the standards or through decision-makers giving weight to the standards when assessing proposals.

A better way forward: from B85 to “Standard Design Vehicle”

Many submitters to the review of the standard have argued against the changes to design vehicles and parking space sizes, citing the negative environmental and built form consequences of designing for larger vehicles. This is pleasing, but I fear risks being dismissed as misunderstanding the role of the standard. Superficially, at least, arguing with the size of the 85th percentile vehicle seems to be arguing with reality itself.

While I agree that the vehicle and space sizes should not be increased, I think the way forward requires a rethink of how the standards are framed. In particular, the definition of the B85 vehicle should be revised to sever its relationship with a statistical measurement.

The subtle distinction we need to acknowledge here is that while the B85 vehicle is nominally representing an 85th percentile vehicle, the nearly 20-year gap in updates to the standard means that the B85 vehicle has not actually represented a statistical reality for some time. Through the latter years of that period, traffic engineers have readily acknowledged that vehicles are, in fact, now larger than the dimensions the standard was based on – yet in practice, we have accepted that it is reasonable to design for this size and let those who want to drive larger vehicles live with the inconvenience that results.

We have, therefore, been designing our built environment for cars about the size of the existing B85 vehicle standard for a long time. It is time to formalise that approach and move away from the conception of design vehicles as a reflection of an ever-shifting statistical measurement. Instead, we should see the design vehicle as embodying an implicit compact between designers, planners, traffic engineers, and drivers: this is the size of vehicle we will accommodate; buy one larger than this and it is your problem.

The B85 vehicle should, therefore, be retained at its current size but renamed to “Standard Design Vehicle” or similar. As a piece of standard-making, this is a move towards consistency and predictability over the chaos of perpetually chasing the latest trends in vehicle design. That this approach will neatly sidestep the dilemma of Standards Australia becoming a de facto policy body will be a secondary benefit.


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