# Operationalizing Dyadic Urban Traffic Interaction Studies: From Theory to Practice
## 4 Results: Aspects of Traffic Interaction Study Design Warranting Trade-Offs
### Choice of Scenarios
#### 4.1.2 Example of Scenario Selection  
Appendices A.1-B.4 showcase various use cases of driver:driver and driver:pedestrian interactions. Here, we outline a \"balanced\" approach to scenario selection and provide examples that illustrate how to streamline scenario selection based on these guidelines, which involves identifying a subset of representative scenarios that align closely with the research objectives while remaining feasible within the study's constraints. Factors such as scenario relevance to the research question, potential for generating impactful insights, and logistical feasibility (e.g., time required, participant burden, and budgetary limits) are critical criteria for prioritization. By focusing on scenarios that address the most pressing aspects of the research question or that are most likely to yield transferable insights, researchers can make informed decisions about where to allocate limited resources effectively. The scenarios highlighted in Figures A1 and A2 refer to interactions between two drivers when they approach one another in an orthogonal (perpendicular) or contra-directional (head-on) manner respectively. In fleshing out the scenarios, the grouping (\"common thread\") applied was the direction of travel of the other car (left, right, or straight) in relation to the ego car. Once these scenarios are thoroughly elaborated, we realize that the 27 total interaction scenarios (18 orthogonal and 9 contra-directional) is a large number of scenarios that may be pragmatically impossible to investigate exhaustively in an interaction study. It therefore becomes necessary to eliminate some scenarios to scope the study to the ones that are the core focus of the research question. For instance, if the research question deals specifically with space sharing conflicts, then there may be an argument to eliminate scenarios in which the cars do not actively cross one another's path even though they encounter one another. Thus, in Figure A1, scenarios DD-O2, O-5, O7, O8, O10, O11, O12, and O14 can be omitted. Similarly, in Figure A2, scenarios DD-C5, C6, C8, and C9 may be ignored. This allows for a more streamlined consideration of the problem space for a focused interaction study. Similarly, Figures A5 and A6 showcase the interactions between a driver and a pedestrian when they approach one another in an orthogonal (perpendicular) or contra-directional (parallel/head-on) manner respectively. Among the 24 total interaction scenarios (12 orthogonal and 12 contra-directional), the research question may help us winnow down the scenarios of interest. For example, if the focus is on how the pedestrian crosses the road when the car approaches from their side regardless of the behavior of the car predicated on its intention (to turn or go straight) at the intersection, the scenarios DP-O1, O2, and O3 essentially reduce to one scenario--for each of them the car approaches the pedestrian from the side. Any one of these three scenarios can be chosen. Consider another study design driven by road geometry: if the road the pedestrian crosses is a single-lane road as opposed to a multi-lane one, scenarios O4, O5, and O6 essentially mirror scenarios O1, O2, and O3 respectively. In each of them, the pedestrian essentially crosses a one-lane road with a car approaching them from the side. This type of rationalizing can help scope the interaction setup into component scenarios that are of interest for the research question. Besides the figures mentioned above, which are full-factorial designs of dyadic interactions between two drivers, or one driver and one pedestrian at an intersection, we also included several other interaction scenarios in the appendix. Figures A3 and A4 highlight non-exhaustive combinations of interaction scenarios in a parking lot and other non-intersection on-road situations respectively for two drivers, and Figures A7 and A8 do the same for driver-pedestrian encounters.