Like PrT assignment procedures (Impedance and VD functions) the PuT assignment procedures derive the impedance of a connection from several skims of this connection or route (PuT skims). Thus, the impedance is a user-defined combination of various skims. According to requirements, a malus or a bonus can be specified for various properties of a connection. The general rule is "The lower the impedance of a connection, the higher its share of the transport demand".
In contrast to PrT, however, the impedance is used not only for the connection search, but also to evaluate the connections during the connection choice by some of the PuT procedures. Impedance can consist of times and fares. Due to the impedance dependency on the temporal utility (Temporal utility) at the connection choice of the timetable-based procedure (Timetable-based assignment), the impedance of a connection can be different from time interval to time interval.
The actual definition of impedance differs in the various assignment procedures. The timetable-based procedure actually uses different approaches in two of the calculation-internal work steps. An overview is given in Table 170. All factors can be set freely and also be set to zero, so that they are not considered in the assignment.
|
Procedure |
Definition of impedance |
|
Timetable-based – Branch&Bound search |
IMP = JRT • Fac1 + NTR • Fac2 + TSysIMP • Fac3 |
|
Timetable-based – Shortest path search |
IMP = JRT |
|
Timetable-based – Choice |
IMP = PJT • Fac1 + Fare • Fac2 + ∆Tearly • Fac3 + ∆Tlate • Fac4 |
|
Headway-based – Search |
IMP = IVT + TWT • Fac1 + NTR • Fac2 Here, TWT represents the expected wait time for the line the passenger wants to board for the transfer. |
|
Headway-based – Choice |
IMP = PJT • Fac1 + Number of fare points or fare • Fac2 |
Table 170: Comparison of the impedance functions in the PuT assignments
