Grids vs cul-de-sacs for suburbs

To celebrate the establishment of the weekly blog, I picked grids and cul-de-sacs for suburbs as the topic which I had mentioned in my final presentation at Griffith University.

The Queensland Department of State Development, Manufacturing, Infrastructure and Planning (2019) was consulting the community to create healthier and more active communities across the State. One of the provisions was to have street patterns based on a grid-like structure to facilitate walkability. The community consultation has closed and the results and final proposal will be published by November.

Before we know what the Government decides, it is a good opportunity to take a look at both road systems from different perspectives.

Connectivity, walkability and road safety

In the last few months, I was involved in letterboxing around suburbs in Labrador, Biggera Waters, Arundel and Parkwood in the City of Gold Coast, Queensland. Two of them were in the grid system and the other two were in the cul-de-sac system. From the perspective of letterboxing (mass delivery), I did think that cul-de-sacs were very convenient. However, is it always the case for other users of the roads and in the neighbourhood?

One big argument is that the grid system provides higher connectivity. For cul-de-sacs, it is an easy fix for pedestrians by adding pedestrian pavements between cul-de-sacs. However, you cannot do that for cars. If you do that, it is not a cul-de-sac any more. This implies a longer travel distance and time from one place to another one (Figure 1). Indeed, the walkable distance is generally lower in the cul-de-sac system than in the grid system (Figure 2).

There are many implications from the connectivity and walkability of roads. Residents are discouraged for walking in cul-de-sacs and they tend to drive to travel around.. Vehicle routes tend to be longer journeys with complications, which further implies other environmental impacts (spoiler: this will be discussed next week). Due to the longer journeys, public transport is generally more costly in cul-de-sacs.

There is always a claim that cul-de-sacs provide the neighbourhood with better road safety because of lower speed at the cul-de-sacs and lower traffic flow. However, the myth seems to be broken by Nielsen (2006) as most of the injuries or deaths associated with children are being backed instead of being driven forward. I think that discouraging speeding and minimising traffic flow do help with road safety, particularly at the end of the cul-de-sacs. However, we also need to acknowledge that it is not always related to the vehicle speed but the awareness of the drivers.

In general, the grid system has higher connectivity and walkability of roads and the cul-de-sac system may provide better road safety.

Figure 1: Grids and cul-de-sacs (connectivity) (Source: Ulrich 2015)

Figure 2: Grids and cul-de-sacs (walkable distance)

Crime prevention

Crime is complex as it is human-based and associated with many other factors. It is also a debatable topic when it comes to the comparison of two systems. Cozens and Hillier (2008) showcase this complicated phenomenon with multiple case studies from other researchers and conclude that the effectiveness of crime prevention for both road systems depends on the types of crime.

That makes sense. Think about when you walk alone along a quiet street. Do you feel safer with or without street light? Do you feel safer with or without street trees? There are many questions and factors associated with the perception. We all have different answers because we are human beings and feel differently. Cul-de-sacs may discourage people to go to the deadends due to one-way entrance/exit and newcomers can be easily spotted; grids filled with pedestrians or direct angles from houses may allow better surveillance from the neighbours (Distel, 2015).

Both systems seem to work regarding crime prevention based on my quick research. I think that we do need to consider the context (socio-economic status, population, etc) of the place before deciding which one to adopt. I think that the grid system gives me and my neighbours a better overview of the situation of the street. At the end of the day, if I could choose, I would prefer trusting myself and my neighbours that may watch the place to trusting a cul-de-sac that possibly discourages the burglars or other criminals from coming to the place.

Energy consumption and interior temperature

Rising temperature is one consideration when (re)developing a community. Despite conducted in an arid city in Argentina, where air conditioning is essential, the research done by Sosa, Correa and Cantón (2018) shows that the grid system has higher energy efficiency. The houses can be positioned for the best angle that can minimise insulation and interior temperature.

Similarly, the Queensland Department of Housing and Public Works (2019) provides resources about sustainable design for housing; design features include building shape, orientation, ventilation, solar access, and construction materials. While that is for a single house, if the road system is designed based on a grid system, the houses generally would face the more ideal orientation (assumption: the orientation is designed correctly).

Along with the rising trend of temperature, it can be foreseen a higher air conditioning usage in suburbs. Regardless, the interior temperature seems to be lower under a grid system. In terms of economic benefits and environmental issues associated with energy consumption/generation, the grid system is a better one.

What do you think?

• Do you think the grid or cul-de-sac system is better?

• What is your priority when it comes to road systems?

Read this post on LinkedIn:

https://www.linkedin.com/pulse/grids-vs-cul-de-sacs-suburbs-dominic-tang/?published=t

References

Cozens, P., & Hillier, D. (2008). The shape of things to come: New urbanism, the grid and the cul-de-sac. International Planning Studies, 13(1), 51-73.

Distel, M. B. (2015). Connectivity, sprawl, and the Cul-de-sac: An Analysis of Cul-de-sacs and Dead-end Streets in Burlington and the Surrounding Suburbs (Honours Thesis, University of Vermont, Burlington, Vermont, United States). Retrieved from https://scholarworks.uvm.edu/cgi/viewcontent.cgi?article=1017&context=castheses

Nielsen, J. (Presenter). (2006). Cul-de-Sacs: Suburban Dream or Dead End? [Audio podcast]. Retrieved from https://www.npr.org/templates/story/story.php?storyId=5455743

Queensland Department of Housing and Public Works. (2019). Resources for sustainable homes. Retrieved from https://www.hpw.qld.gov.au/construction/Sustainability/SmartSustainableHomes/SustainableHomeResources/Pages/Default.aspx

Queensland Department of State Development, Manufacturing, Infrastructure and Planning. (2019). Creating healthy and active communities. Retrieved from https://haveyoursay.dsdmip.qld.gov.au/creating-healthy-communities

Sosa, M. B., Correa, E. N., & Cantón, M. A. (2018). Neighborhood designs for low-density social housing energy efficiency: Case study of an arid city in Argentina. Energy & Buildings, 169, 137-146.

Ulrich, S. (2015). Planning for Health: The Healthy Places Program at Columbus Public Health. Retrieved from https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/9/3820/files/2015/10/OSU-Intro-to-Planning-Healthy-Neighborhoods-25vbjfy.pdf