Has Transport Planning been forgotten in the new Census?

23 Mar 21

TRICS is a nationally recognised system of trip generation used throughout the UK. It is an integral part of the transport planning process, and indeed in most cases a vehicular trip rate from TRICS is applied to the Census data to determine the multi-modal trip generation. However, the TRICS database also contains multi-modal trip rates which will provide this generation directly without the need for Census data. Is this the way forward? This method of assessment was available previously, even if not necessarily the preferred method, as the most relevant sites in terms of development type, size and location may have quite different mode shares to the development site.

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At least we were all given something to do whilst stuck indoors this past weekend – Sunday was Census day, and I’m sure all of you would have enjoyed answering questions about your current situation…. which is obviously very different to what it would have been 1 year ago, let alone 10 years ago! In 2011 we were going through a recession, which may have impacted how we answered the questions but is unlikely to have affected the percentage travel by each mode dramatically. This time round we have a global pandemic with residents encouraged to work at home and many local facilities shut; this will definitely have an impact. We also can’t help but wonder if this could be the last census before we start to see Carbon Footprint questions being included (electric or petrol car ownership, cycle ownership etc?), but that is a thought for another day. However, the key question that stood out by far to us in Iceni Transport was ‘How do you usually travel to work?’.

You may or may not be aware, but this question has played a fundamental role in transport planning. Typically, to determine the multi-modal trip generation of a forthcoming development, the travel to work data for the local census area (middle super output area [MSOA]) within which the site is located is applied to the proposals in order to split the expected trips across the different modes. This then tells us how many people are expected to drive, walk, cycle, use the bus, get the train etc to and from a development site. Whilst the use of 2011 data has been scrutinised in recent years given its age, it is still widely used to determine multi-modal trip generation for a wide range of applications, and resultingly to plan new infrastructure or improvements to existing infrastructure. For example, the Census data could be applied to a 1,000 unit scheme next to a tube station in London to determine how many extra rail trips are expected as a result, and any improvements considered to be required would be based on that number.

The following guidance was what really set the alarm bells ringing for us in Iceni Transport – ‘If the coronavirus pandemic has affected how you travel to work, select the answer that best describes your current circumstances’. Given a high number of us will be reading this article whilst sat working from home, the percentages are likely to be very heavily weighted towards the ‘Work mainly at or from home’ answer. Whilst Covid-19 is likely to change travel habits and result in a ‘new normal’ we are not sure that there will be quite the reliance on working from home in future years as there is in March 2021. This presents a few initial questions:

• Will the data from Census 2021 on method of travel to work be of any use in future transport planning?
• Would highway authorities accept the use of 2021 data given this, and at the same time would they continue to accept 2011 data with it now being more than 10 years out of date?
• Do we think that the use of Census method of travel to work data is still appropriate?

The last question is key, and it will be interesting to see how we as an industry undertake our trip generation assessments going forwards? Is there now the realisation that the previous methodology of relying on the Census, a data source that is only updated once every 10 years and is based on information at that exact period, may not be the most reliable or practical way to predict future travel habits. Not only this, but the Census data limits movements to work only, yet a number of other trips are made outside of the journey to and from work. Should we instead be looking at alternative methodologies? A couple of early thoughts on what these are and what they could look like are as follows:

• Could there be more emphasis on Travel Plan data? Given planning conditions / S106 requirements of new developments, there should be an abundance of schemes with annual / bi-annual travel plan data showing realistic and up-to-date travel habits of local residents. Can we use this information instead? Should there be a resource which makes this information more publicly available?
• Should we think about localised multi-modal surveys in the area of the development for similar land uses?
• The Office for National Statistics (ONS) have acknowledged that the travel to work question may cause issues and have stated on their website that they are intending to ‘look at other ways of meeting this data need’. It will be interesting to see what this means and what they intend to do – will there be a follow up survey in 2022 (noting that Scotland have delayed their Census until next year) to fact check? It may perhaps be interesting to have a new survey in 2022 to compare the three datasets – the 2011 ‘normal’ data, the 2021 ‘pandemic’ data and then the 2022 ‘new normal’ data. This could show whether people have reverted back to their old ways, or if the habits developed during the pandemic have stuck.
• Will there be a future reliance on mobile phone data and can this provide the information we require instead?
• Or is there an alternative methodology to be used for trip generation within TRICS?

TRICS is a nationally recognised system of trip generation used throughout the UK. It is an integral part of the transport planning process, and indeed in most cases a vehicular trip rate from TRICS is applied to the Census data to determine the multi-modal trip generation. However, the TRICS database also contains multi-modal trip rates which will provide this generation directly without the need for Census data. Is this the way forward? This method of assessment was available previously, even if not necessarily the preferred method, as the most relevant sites in terms of development type, size and location may have quite different mode shares to the development site.

Interestingly, earlier this year the TRICS consortium released new guidance on how trip generation should be calculated, referencing a new ‘Decide and Provide’ approach. This guidance recommended that, rather than primarily basing future predictions on past conditions, more knowledgeable assumptions should be made, with appropriate consideration given to the detail and design of the scheme being proposed, additional development coming forward in the area, changes to transport infrastructure, and consequently, evolving travel habits.

Iceni Transport are continuing to monitor the situation and establish the best way to assess trip generation which will vary depending on the client, available data and local area. Whilst localised surveys appear to be the most logical conclusion these won’t always be relevant or cost effective and, as such, Iceni need to do what they do best – deliver the most appropriate solution for the client’s consideration. We would be happy to discuss these thoughts with you further should you be interested.

Richard Jay Senior Transport Planner,Transport

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