We estimate that there is a net benefit of 67p to society for every mile cycled rather than driven. Putting a figure on the value of cycling in this way could offer a lot in terms of helping politicians, practitioners and the public to understand the relative cost of their modal choices.
We recently published a family of Bike Life reports with the city authorities in Belfast, Birmingham, Bristol, Edinburgh, Cardiff, Greater Manchester and Newcastle.
These reports included a value of societal gain for every mile that is cycled instead of driven. In this blog I will take you through my calculations and how we arrived at this figure.
The societal gain model is an innovative model developed by Sustrans as part of the Bike Life project. It builds on work originally developed for the Copenhagen Bicycle Account.
A preliminary set of unit values was generated that estimate the benefits and costs of cycling, and the benefits and costs of driving. The two outputs are common across the seven Bike Life partner cities; that is to say we haven't been able to refine the approach sufficiently at this stage to generate different values for the different cities.
The unit costs consist of two parts:
- the benefit or cost to the individual user, and
- the impact on society.
In economic terms these are referred to as internalised and externalised costs. Internalised costs include time cost, vehicle operating costs, and personal health impacts.
Externalised costs include expenses in connection with congestion, noise, air quality and emissions, wider public health and accidents.
Some variables can have both internalised and externalised costs. This is broadly the approach used by the UK Government in estimating the value schemes (e.g. in the context of generating benefit to cost ratios for scheme appraisal). However, our approach is very definitely not in line with how the appraisal tool, WebTAG, is intended to be used.
Nevertheless, we can come up with some figures...
The value of cycling formula
There is a cost to society for every mile cycled of 28p, whereas the cost per mile driven is 95p, more than three times as much. There is a difference of 67p between the cost per mile cycled and the cost per mile driven. We call this difference, the 67p, the value to society of cycling a mile above driving a mile. Estimating a proportion of miles cycled rather than driven, enables us to calculate the economic gain of cycling to society.
The formula for the saving to individuals and to the local economy for every mile biked instead of driven (or the value of cycling to society), in its simplest form, is therefore:
([Cost per mile driven] – [Cost per mile cycled]) * [Number of miles cycled rather than driven] = [Value to society of miles cycled rather than driven]
The number of miles cycled rather than driven comes from a very simple estimate of the number of miles cycled multiplied by percentage of car ownership. This doesn't include miles cycled for leisure.
Cycling net benefit by city
Using the above formula, we made calculations for the seven Bike Life cities:
The values are a function of levels of cycling, population size, and car ownership levels. Figures for investment in cycling fall way short of the values of societal benefit, particularly when taken over several years of course.
The cost of cycling
We have calculated the value of cycling, but how do we end up with a net cost per mile cycled? Calculating the cost is down to the old values of time problem. These figures are calculated using values of time in WebTAG during 2015.
Both driving and cycling carry a time cost. Without the value of time, there is a net benefit value around 50p per mile cycled (largely a derivative of health benefits). The net cost of driving, without the time cost, is around 76p per mile. Recent recommendations to change WebTAG values of time will change the values but we haven't done the work to recalculate the values as yet.
Work in progress - we'd like to hear from you
Our approach offers a lot in terms of helping people understand the relative cost of their transport choices. But I appreciate that we are dragging WebTAG in a direction that is not intended. We are working to develop this approach in anticipation of the production of the 2017 round of Bike Life reports.
We will be very interested to hear about ideas for possible changes in respect of the accounted variables, different value sources for the variables, alternative variables that we might include, or different approaches to capturing an expression of value to society. Also, whether different cities should have different values, and how these might be derived, is a question we will be looking at.
If you have any ideas on how we can build on this approach, please email Dr Andy Cope.