Network Rail's Rail Utilisation Studies refer to "non-user benefits", though they do not appear to explain how these are measured. There doesn't seem to be a clear explanation on the internet either, so perhaps someone could shed light on this.
As an example: the Brighton main line is closed for about ten weekends a year for maintenance. This has an effect on the economy of the city - for instance, shops and restuarants do less business. In turn, this depresses rental values, and in theory , the effect could be estimated.
Another more significant example concerns the Jubilee Line extension, which, according to a survey conducted for Transport for London, resulted in a aggregate increase in land values of around three times the construction costs.
Is this the kind of thing that is being referred to under the heading of non-user benefits? These are critically important because they set the bar which determines which schemes are worth proceeding with and which are not.