Heathrow Airport Redevelopment Study
Background - the London airport question
There is a debate underway in London about how to meet the expected growth in demand for air travel in the coming years. Heathrow is the city's largest airport but it occupies a constrained site where growth would be difficult. See the vburbandesign blog for more background and comment.
One option under review is to build a new hub airport on an unconstrained site outside the city. This would provide relief from aircraft noise for thousands of residents of west London, and accommodate significant growth for the foreseeable future, but the price of construction and relocation would be high. The concept has been supported by several engineers, architects and planners who have worked up proposals for a new airport, and have considered what would happen to the existing Heathrow site.
Holistic City Limited collaborated with Spiros Karakostas of Seed, developer of customized spatial optimization algorithms, to undertake a study of the Heathrow site and demonstrate how spatial optimization technology could provide insight into a large scale masterplan.
Overview of assumptions:
- The total quantity of development is approximately the same as that suggested in the Heathrow Garden City proposal by Graeme Bell of the Town and Country Planning Association of May 2012. The model aims for a total of approximately 30,000 residents and 80,000 jobs. (The large size of the site means that the total quantities could be much higher or lower depending on the density of development chosen).
- Four different land uses were used in the model - a) open green space, b) low density residential, c) low density commercial uses and d) high density mixed uses.
- Three design criteria were introduced (to be maximized): achieved (total) land value, contiguity of proposed maps and compatibility of adjacent land uses.
Of these criteria, land value is primarily governed by the following spatial rules:
- Low density residential land values would be adjusted upwards significantly if near (but not immediately adjacent to) a tube station.
- Low density residential land values would be adjusted upwards if near open green space.
- Low density commercial land values would be adjusted upwards if near roads and, to a lesser extent, tube stations.
- High density mixed use land values would be adjusted upwards significantly if near a tube station and, to a lesser extent, roads.
The optimization algorithm was used to generate optimal maps by either incorporating different weighting schemes for each design criterion, or simultaneously evaluating all criteria on a Pareto basis.
The map below shows the layout generated to maximize the total land value of the development across the whole site.
The optimized map provides some interesting results:
- As expected, development was concentrated around the four main tube stations (yellow dots on the map).
- The higher value of the high density mixed use developments took priority in the areas immediately around the tube stations.
- Lower density commercial uses extended along the roads, particularly at the south-west and south-east corners of the site.
- Residential uses were concentrated around the tube stations up to a point, but then were developed into elongated residential sites projecting out into the green spaces. This maximized the number of houses adjacent to open green space to increase the overall land value of the layout.
- Alternatively, if the design criterion on contiguity (or compatibility) is also taken into account, different spatial allocations are proposed.
In summary, we believe that generative approaches can play a valuable role as part of a wider masterplanning effort.
The results of generative studies should always be treated with caution and be reviewed critically, but they can provide objective validation of instinctive assumptions and in some cases they may throw up successful options that could have been completely overlooked by a conventional design process.