Designing transport for the places we really want to live

A new paper from urban design research charity Create Streets argues we are currently spending huge amounts of money on a single solution to transport – new roads – with decisions driven by outdated and crude spreadsheet models and a focus on the wrong metrics of success.

Author David Milner, Create Streets’ Deputy Director, says “We treat the results of transport prediction models as an uncontested fact, yet they are neither sophisticated enough to balance all the ways in which we travel around nor agile enough to adapt to changing technology and human behaviour. We must change how we use them so we can design the infrastructure we really need.”

In the briefing paper Computer Says Road: why outdated transport models ruin new developments and how to fix them, Milner says the way we currently plan transport infrastructure still produces ‘big road urbanism’. And “instead of assuming wider roads are always the answer, we should tackle the problem of how people travel around by using a full toolbox of solutions, from investing in a range of transport options to putting the services we use at the heart of new developments.”

This, he adds would keep people moving while supporting happier, healthier and better towns and cities at lower cost. “Instead of spending tens of millions of pounds on one junction or on widening a few miles of road, we should instead design better places where more journeys are by foot, bike or public transport. We can do this by siting amenities we want to visit in the heart of new developments, not their perimeters.

Computer Says Road sets out how we currently plan transport infrastructure and identifies six key issues where the established approach falls down and in each case proposes solutions.

The six issues and solutions covered within the paper are:

Issue 1: The wrong models – existing traffic modelling, so called ‘Predict and Provide’ is outdated and based on flawed, oversimplified solutions. “We have outsourced the responsibility to spreadsheets,” says Milner. “We are too focussed on a single solution. Decisions are made by outdated models based on old data and even older human assumptions. The models compound poor assumptions and repeatedly prove inaccurate, as can be seen by comparing the DfT’s own forecasts with actual results. 

Solution 1: Dispense with ‘Predict and Provide’ and adopt the ‘Vision and Validate’ methodology for all schemes. Plan for the traffic and place your residents want. Once you know the desired outcomes, work back from this by planning the travel we want and need to meet our health, happiness and environmental goals.

Issue 2: Valuing algorithms over expertise. Decision makers treat traffic models as a fact rather than an opinion. “If the computer says ‘road’, it must be done,” says Milner. But the solution pumped out at the end is only as good as the information fed in at the beginning. And that information is vulnerable to mistakes and human biases.

Solution 2: Give traffic models the same weight as an expert opinion from your design team rather than as an exact science. “Challenge it, unpick it, understand it. It is just an opinion, it’s not a binary decision, it’s not true or false” urges Milner.

Issue 3: Valuing traffic congestion over everything else. The Department for Transport’s cost-benefit analysis tool known as Transport Analysis Guidance (TAG) fails to value social and environmental benefits and costs, and overvalues travel time, Milner explains. TAG, which gives highways authorities a costed appraisal for proposed transport schemes, “needs to be dragged kicking and screaming into the 21st century. It fails to properly capture non-travel-time benefits, such as health, wellbeing and the environment, so the answer will always be to build more or bigger roads. The staggering value we put on improving journey times by just a slight amount versus any social or environmental impact is laid bare deep inside the TAG spreadsheet. The external cost attributed to severe road congestion is valued at 57.2 pence per km travelled, whereas excess noise is costed at 0.1 pence per km. Air quality is valued at 0.5 pence per km and greenhouse gases stand at 2.8 pence per km. This means all of these harms combined are given just 5 percent of the value of congestion on our roads.”

Solution 3a: Update TAG to redress the balance in favour of health, wellbeing, climate and happiness and monetise negative environmental and social costs. As Milner points out “policy already supports rebalancing the benefits beyond saving a few minutes from your daily commute – but the TAG hasn’t caught up yet.”

Solution 3b: Do not use TAG at the design stage of a project, instead use it to compare detailed design options at a later stage. The design team and transport planners should decide when new road infrastructure is needed. Only then should TAG be used to compare detailed plans of road schemes.

Issue 4: Valuing commuters over everyone else. We place an astronomical value on relieving just a few minutes of congestion, mostly occurring during the morning and evening commute. This is despite the fact that commuting accounts for just 15 per cent of trips. This results in roads designed for a brief moment in the day and leaves vast amounts of road capacity idle for the rest of the day.

Solution 4: Plan for the whole day, not just peak hours. “We should end our obsession with optimising transport between 08:30 and 09:30,” says Milner. “Covid has accelerated the change in work patterns and we need to catch up with the new reality of flexible working. Post-Covid commuting patterns mean that thousands of homes could be built without anywhere near as much expensive new road infrastructure as current models ask for. This would speed up the delivery of new homes at a time that they are desperately needed.”

Issue 5: Failing to consider systemic impacts. “Our transport infrastructure is a series of expensive disjointed projects. The way we move around is designed in a piecemeal way, project by project: a link road here, a new junction there, each project often independent of the rest and not considered in a holistic manner.” 

Solution 5: Treat movement (not transport) as a strategic outcome, not a series of disjointed infrastructure projects. “Building another road shouldn’t be the expensive default solution for every congestion challenge,” urges Milner. Instead, all towns and boroughs must consider transport as a holistic ecosystem and apply a range of solutions to achieve their desired outcomes. 

Issue 6: Garbage in equals garbage out. “The data we feed into existing traffic models is often crude, unintelligent and outdated,” he adds. “The models takes no account of the number of passengers in the vehicle, or whether it’s a bus, an Uber or a cargo bike. It also ignores the family of four walking alongside the pavement. The inevitable result of feeding these crude numbers into traffic models is the model identifies the need for more capacity for vehicles.”

Solution 6: Count people not cars. Acquire better real-time data on how people move, not just individual vehicles. Use artificial intelligence and machine learning to analyse it and inform smarter infrastructure provision. 

Milner describes the paper as a “plea to stop making society a servant to computer models” and says “we should agree on the outcome we want first, then use data and specialists to refine our designs and make it happen in an effective way.” 

He ends on a positive note, “There is reason to be optimistic. Residents, councillors and developers I speak to across the political board are mostly in favour of spending less on tarmac and more on our neighbourhoods, trees, schools, buses and high streets. The challenge now is to give them the tools, update the policy and let them get on with creating the places we all want to live in.” 

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