More on on-site car parking and decision making

A couple of blogs back I started to look at the question of how to assess the effects (consequences) of an on-site parking shortfall for a housing development in a Special Character Area in the inner suburbs of Auckland. I want to do this to better understand decision making, rather than look at the details of the specific case.

I started with the proposition that I would try to understand the nature of the effects and the state of the environment impacted by those effects. Next step would then be to consider the significance or consequences of the effect by looking at the relevant planning documents.
The case study involves a 19 dwelling development with 9 on-site car parks, a short fall of 10, based on the  Auckland Unitary Plan requirement of 1 on-site space per dwelling.

First, I tried to gauge car ownership based on 2013 stats data on the number of cars per dwelling, taking into account bedroom numbers and locality.  I also tried to guess the 'state' of the on-street parking resource in the area.

I came up with the following 'effects' of the proposed development:

1. Number of extra cars in the neighbourhood = 22
2. Number of extra cars looking for kerb side parking = 13
3. Reduction in cars in the region due to inner city location compared to if dwellings were located on the edge of the region = 4
4. Higher rates of public transport use (around a 15 percentage point increase) and lower vehicle kilometres travelled (perhaps 20% less) compared to if dwellings were located elsewhere
5. Increased pressure on existing residents in the area to find street parking spaces and hence more pressure to accommodate cars on site, possibly affecting special character values of the environment. 
6. There may be increased demand for car sharing type services, if parking gets harder to find and so people decide to get by with fewer cars. 

Something I missed was the amount of developable space 'freed up' by not having so much on-site space taken up by car parking. Each car parking space occupies about 25 to 30 square metres of land area by the time you take into account manoeuvring area. 19 units are proposed requiring 19 car parks. 9 on-site car parks are to be provided, meaning that space for 10 cars would need to be found. 10 car parks might occupy up to 250 to 300 square metres of space. This is probably equal to at least 2 small dwellings or 1 larger dwelling So a further consequence of having less on-site car parking is having two more dwellings to add to regional housing supply.

The effects are a mix of transport, amenity, and urban form and function effects. They span local and regional scales. The effects are not just about local on-street parking demand and supply. This is pretty typical of RMA and urban planning matters - things are connected.

They are not effects that are in addition to, or more than what might otherwise be expected. They are the 'full' effects, as best as can be estimated. However I did speculate what might be a realistic alternative proposition to give some context to the effects.

The state of the receiving environment is harder to gauge. I estimated that street parking was in high demand, and that over time street parking is coming under pressure through gradual infill and redevelopment, although car ownership rates are dropping. There is also demand from visitors to nearby commercial areas and commuters. I also speculated that the surrounding urban environment was sensitive to pressure to incorporate more on-site car parking on sites, with older villas and bungalows present.

The  consideration of effects has lead to a couple of preliminary thoughts about decision making, and before looking the AUP it is worth exploring these a bit more.

To begin with, the AUP has set in place one decision making 'trigger'. Put another way, there  would be no need to consider all these effects and their connections if either of two conditions existed:

• Firstly, if the development provided the required number of on-site car parks, then all of the other related effects of transport, urban form and amenity fall away from consideration, even if the development adds to street parking demands or fewer houses are built; or
• Secondly, if there was plenty of on-street parking available, then the pressure created by the development for more use of street parking doesn't matter, and again there is no need to consider the other related effects and their consequences.

Decision making triggers are supposed to  be set so that when some condition is exceeded, then investigation and action is needed. Whether the plan has the right trigger is not clear to me. Decision making trigger points should be based on the boundary between a stable (or desirable) and an unstable (or undesirable) environmental state. For example, would a better trigger point be that when street parking reaches 70% saturation, then developments that do not provide on-site parking need to be looked at in more detail? But then that is not easy to measure.

Where there are multiple objectives involved (urban form, transport, amenity) and there is some competition between the objectives, then does the decision making trigger point need to involve some built in (or apriori) trading off between the variables?  Has this been done?

Furthermore, if the decision making conditions are triggered, then there is a presumption that the pressure exerted on street parking from less on-site parking needs to be 'managed' in some way to maintain the stability and integrity of the system or environment. This is a big assumption. In one conception, street parking is a public resource, and like all public resources, it is a resource that can be easily over used to the detriment of all. Is there a value-based judgement to be made that street parking should be 'allocated' fairly?

Another  viewpoint may be that overuse can see flow on or spill over effects to amenity and the quality of the built environment in the area. But equally there are a bunch of benefits to the regional housing market and the regional transport system from allowing more housing in inner city areas where street parking resources are under pressure. 

Final question: do you always need an alternative scenario to help set the effects in context? Decision making theory talks about the importance of the 'counter factual' - for example the environment without the development in place. Something will happen on the site in question, but what might happen? It is important to describe the counter factual accurately and to use it consistently, as the positive and negative effects of the development should be placed in context against the counter factual. Identifying the future without the project is often not straightforward, in particular where the environment is likely to evolve overtime. Does the plan enable a good estimate to be made of the future without the project?  The plan may set a clear 'permitted baseline' which can be taken into account, but what if that baseline is not clear, or is so limited in extent it doesn't provide a realistic 'counter factual'?