On September 17 2023, Wales became the first country in the UK to introduce a default speed limit of 20 miles per hour into law. Although the Welsh Government have highlighted the perceived benefits, the introduction of the new default speed limit has met with some strong opposition. This investigation using System Dynamics will look at the qualitative data using Causal Loop Diagrams to understand the perceived benefits, investigate the opposing views and identify where data can be quantified and analysed using simulation models.