Royal Town Planning Institute Net Zero Transport Research


City Science, in partnership with Vectos, were commissioned by the Royal Town Planning Institute (RTPI) to investigate place-based transport carbon generation and research the contribution of spatial planning and place-based solutions to the goal of transport decarbonisation, through consideration and development of emissions reduction pathways for four different UK settlement typologies.

Our commission was based on previous work developing transport decarbonisation models and scenarios for Local Authorities (e.g. Somerset County Council), utilising our web-based Transport Decarbonisation Tool developed for the Department for Transport. Through consideration of four UK ‘place typologies,’ which accounted for the diverse mix of communities across England, we developed a series of decarbonisation pathways and tested 40 carbon intervention measures to review their relative ability to achieve an 80% reduction in surface transport emissions by 2030, on a pathway to net zero by 2050. Technical outputs included an extensive literature review, carbon accounting for transport and spatial planning interventions and co-author of the research paper.



Transport remains the largest contributor to the UK’s greenhouse gas emissions, with an average contribution of around 35.5% of all emissions for an average local authority (City Science, 2020). Given this challenge and the need to fulfil many local authorities’ ambitions to achieve net zero by 2030, the RTPI commissioned us to catalyse structural change in the spatial planning system to embed a ‘place-based’ approach fully integrated with local transport decarbonisation needs.

City Science Response

We worked in partnership with LDA Design and Vectos by initially undertaking a comprehensive literature and research review, such as from the Committee on Climate Change and the Intergovernmental Panel on Climate Change, before supporting development of four initial spatial typologies. These typologies were typical of real places in England, and included a unicentric city, a polycentric conurbation, a regeneration town, and a growing county. We developed a transport carbon inventory for each of these typologies through disaggregating local authority carbon emission data to local travel behaviour, such as average journey length and mode share.

In order to inform our transport carbon estimates, we reached out to a representative local authority for each of the typologies and gained access to their SATURN highway modelling forecasts. The work included using our Transport Decarbonisation Tool, which we developed with funding from the DfT, in order to appraise the incremental carbon impacts of each option.

City Science Multi-Criteria Appraisal Framework
The four place typologies, Polycentric Concurbation, Unicentric Regional Centre, Regeneration Town, Growing County.

Through extensive stakeholder engagement and partnership working, we then developed forty carbon reduction transport interventions based on the key principles of:

  • Avoid: Maximising localised trips or through alternative digital means
  • Shift: Promoting modal shift away from cars to active travel and public transport
  • Improve: Switching from petrol and diesel to zero emission vehicles (electrification and zero carbon fuelling of private vehicles, public transport and freight)

We modelled tailored interventions as a cumulative package (based on academic and real-word evidence) across each of the four place typologies to demonstrate how an 80% carbon reduction could be achieved by 2030. This modelling of transport carbon propensity, included applying a mixed effects linear model to estimate and forecast the effects of fixed socioeconomic factors and random geographically related factors. Our methodology reflected the needs of diverse settlement typologies, producing each a bespoke holistic decarbonisation pathway to zero emission surface transport.

Decarbnisation pathway exaple for the 'Wooten City-Region'
Decarbnisation pathway example for the 'Wooten City-Region'


We co-authored the research paper which demonstrated a need to break with the conventional planning system approach of meeting predicted changes in travel demand with new road capacity, by focusing instead on integrating land use and transport to enable place-based transport decarbonisation. It also highlighted the wider need to put carbon reduction at the heart of local policy, planning and decision-making frameworks.

The research obtained high-profile national coverage and place-based solutions through the planning process were embedded as a core principle of the DfT’s Transport Decarbonisation Plan.

You can download a copy of the research paper here.

To add further detail to strategies for decarbonisation through fuel switching, we also developed a white paper setting out recommendations for Local Authorities to decarbonise personal vehicles, buses and freight.

You can download a copy of our white paper here.