## 3 Results
### Causal Condition: Current Types of Tyre Procurement  
As mentioned in Section 1.4, Germany's public procurement takes place at the level of the federal government, states, municipalities, cities, as well as through separate organisations in the cities. According to Tables 2 and 3, the interview series took this diversity into account. As a starting point, principal issues were discussed in the interview on #1. In this context, general observations were shared, focusing mainly on public procurement by big national organizations for several ministries. Figure 2: Modified Grounded Theory model of this study. Based on the interview series as a whole, six patterns of public tyre procurement could be derived: three basic types, which differ regarding the extent and complexity of the procurement processes (central cross-application of tyre procurement and awarding of supply contracts; tyre procurement of mixed volume by cities and counties, and finally, tyre procurement by public companies), tyre procurement for specific applications (for the police, cleaning and disposal vehicles) as well as tyre procurement as part of vehicle procurement and leasing. Table 3 assigns the cases to these clusters (multiple assignments possible). Basic type B1--Central cross-application of tyre procurement and awarding of supply contracts: Centralised contracting was reported in six interviews (on cases #2, #5, #6, #7, #8, #16). The cases include, for example, the central procurement office of a German Federal State and the central purchase of the police in two States. Their procurement volume is several thousand tyres per year, respectively. Their organisations use EU-wide tenders for tyre procurement. One interviewee explained:  
_'Public procurement law distinguishes between lower and upper thresholds. The EU announces the threshold value of the contract every two years. Currently, it is EUR 214,000. If the amount is higher over the entire contract period, then I am obliged to to issue a European call for tender. '_  
In one case, different procurement processes are used on the EU and national levels, depending on each process's financial volume. One interviewee provided a detailed example of a procurement process:  
_'Type procurement takes place [... ] with several economic operators. [... ] In the process, we work with several hundred offices or departments. All common brands and producers are included. [... ] On this basis, the users are given the right to choose, based on various criteria [... ]. A list of criteria was tendered, and bidders indicated what they could meet. '_  
Various criteria are used in the procurement processes. The most comprehensive overview was given by the interviewee of case #8, see Box 3. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Tyre procurement Cluster** & **Procurement Situation** & **Cases * \\ \hline \multirow{8}{*}{B—Basis types} & B1—Central cross-application of tyre procurement and awarding of supply contracts & \\  & B2—Tyre procurement of mixed volume by cities and counties & 10, 12, 13, 14, 15, 18, 19, 20 \\ \cline{2-3}  & B3—Public type procurement by public companies & 3, 4, 9, 11, 17, 21 \\ \hline \multirow{8}{*}{S—Specific applications} & S1—Tyre procurement for the police & 5, 6, 7 \\ \cline{2-3}  & S2—Public type procurement for cleaning and disposal vehicles & 3, 4, 11, 12, 17, 21 \\ \hline T\&L—Tyre procurement as part of vehicle procurement \& leasing vehicles including tyres & 22 \\ \hline \hline \end{tabular}  
* Case 1 included various types of clusters and was not classified specifically.  
\end{table} 
Table 3: Summary of the procurement situations in the interviews. Basic types B2 and B3--Tyre procurement of mixed volume by cities, counties, and public companies: The interviews on the city and county levels referred to tyre procurement in high and low quantities, providing particular insight into volume-related differences in the CPP processes, also compared with big EU-level tenders.