## 3 Space-Time Transport Performance Measure (_STTP_)
### Calculation of _Sttp_  
_STTP_ (Formula (1)) is calculated by following three steps: (A) the setup of the _STPA_; (B) the calculation of the _IDTC_ figures; (C) the calculation of the _IDD_ figures. (A) The setup of the _STPA_ is made in the same way as for _STA_. The daily sequence of fixed activities (\(a_{1-n}\)) constrained in space and time for the observed individual is schematised. This includes the location where each \(a\) takes place (address); its category (home-stay, work, education or other); the duration of each \(a\) given by its mandatory starting and ending time; the transport mode(s) usually used to travel between each couple of subsequent activities (\(a\)); and the degree of fixity for each \(a_{n}\) according to the flexibility of its location and timing. This is made through a 1-5 Likert scale, where 1 indicates maximum flexibility of the location and/or timing of \(a\), while 5 shows a minimum one. The data needed to reconstruct the _STPA_ are collected from observed individuals using travel diaries. Interviewed individuals are asked to fill them out by considering a typical weekday of their daily life. Table 2 shows an exemplificative (and fictional) _STPA_. Figure 1: Relation between _STA_ (**left**) and _STTP_ (**right**) and their key features. (B) Once the _STPA_ is set, _IDTC_ is calculated (Formula (2)). _IDTC_ is the sum of the Individual Transport Costs incurred by an individual for each daily travel performed by the transport mode \(k\) between each couple of subsequent fixed activities _a,a+1_ (_ITC\({}^{k}\)\({}_{a,a+1}\)_). Each _ITC\({}^{k}\)\({}_{a,a+1}\)_ value is calculated through a generalised cost function, including a series of monetary and non-monetary (but monetizable) costs [42]. This consists of the monetary cost of travel (_Cm_), the cost of the in-vehicle travel time (_Civtt_), and the cost of out-of-vehicle travel time (_Covtt_). _Cm_ encompasses the costs for the usage of infrastructures (e.g., tolls and parking fares), the operating costs of vehicles (e.g., fuel, usage-related depreciation and insurance), and the costs for access to services (e.g., public transport; from now on PT). _Civtt_ includes the time spent within private, shared or pooled vehicles. _Covtt_ covers the cost of the time to access the first transport system (first mile), the waiting time for transport services, the transfer time among transport services, and the time to reach the final destination (last mile [42]). _Civtt_ and _Covtt_ are monetised based on unitary Values of Travel Time (_VTT_). As demonstrated in the literature, _VTT_ may vary by income, country, travel purpose, mode of transport and distance. It depends on the approach with which it is estimated (e.g., stated vs. revealed preference surveys [44]). The wage rate method is used for _STTP_: different wage rate shares are assumed depending on the country of investigation, travel purpose, and transport mode. Moreover, the actual wage rates of observed individuals are used to make the estimation individual. (C) Once _IDTC_ is calculated, this has to be weighed against _IDD_ (Formula (3)). This is the sum of the distances measured between each couple of subsequent fixed activities _a,a+1_ (_D\({}_{a,a+1}\)_). Each _D\({}_{a,a+1}\)_ value is measured as Euclidean and not travelled distance along with the transport network. Indeed, the travelled distance may be influenced by the design of the transport system and not only by the land-use system. For instance, this is the case with fast transport systems such as motorways and high-speed railways, which tend to generate much more detours than slower systems (a phenomenon called \"spatial inversion\" by [PERSON] [45]). This detour is an aspect that transport planners can potentially address e.g., by modifying the shape of the PT lines and distribution of stops. Therefore, it is a factor to be included in the accessibility computation.