From the point of view of public health and the environment, it can be argued that people who spontaneously walk great distances display a desirable behaviour, whereas those who drive a car without any walking in public space do not. A suggested metric can describe the relationship between these two behaviours within a conurbation, with a view to informing public policy. The Swiss transport and mobility micro-survey is based on a representative sample of the general population, who were asked about their mobility behaviour on a reference day. In 2010, the 62'868 surveyed persons walked on average 1.7 km. However, analysis of the data shows a shockingly skewed distribution. Fully 38% of survey respondees did not walk on the reference day (only trips > 25 metres outside buildings or premises were considered). Among these, around 11.5% (of the total sample) stayed at home, 22.5% drove a car or motorbike without any walking in public space, and a further 4% rode a bicycle without walking. At the other end of the spectrum, around 13% of the sample were found to walk over 5 km. For this segment, we have coined the expressions "great walkers" or "frequent walkers". We suggest the creation of a new metric, which is the proportion of people walking > 3 km on the reference day (thereby exceeding WHO guidelines), divided by the proportion of people driving a motorised vehicle without any walking in public space. Because these two groups exist in roughly equal proportions in Switzerland, the value of this metric is equal to 1 for the whole country. The metric is specific and time-bound (the survey is repeated every 5 years). It is relatively easy to calculate and the basic data are available. It deals away with the problem of defining a denominator since it is a ratio of two quantities which are investigated in the same way, on the same population. Especially, it can be seen at first glance whether frequent walkers are more prevalent than non-walking drivers (metric > 1) or the opposite (metric < 1). We therefore believe that it will be useful for planners and decision-makers. Preliminary analysis on the 50 conurbations in Switzerland shows that the new metric discriminates well between conurbations. The implications for policy are discussed, in the context of Switzerland which is a decentralised country where most walking-related policy is decided and rolled out at the level of cantons, communes and/or conurbations. The results are discussed in the light of two reviews of urban sustainable development indicators (Tanguay et al. 2010; Mori and Christodoulou 2012) which reveal a general lack of consensus as well as problems surrounding the accessibility of data on which to base the indicators. We suggest that the new metric describing frequent walkers/non-walking drivers be integrated into the leading urban sustainable development indicator systems, most of which, as yet, contain very little on walking.